{"id":7454,"date":"2026-09-10T21:08:52","date_gmt":"2026-09-10T20:08:52","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/"},"modified":"2026-09-22T12:46:14","modified_gmt":"2026-09-22T11:46:14","slug":"flue-gas-desulfurisation","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/","title":{"rendered":"Flue-Gas Desulfurisation"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-oxides-of-sulfur-page\">\n  <style>\n    .ols-revision-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --soft-blue: #eef4ff;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-green: #f0f7f1;\n      --green: #3f8f46;\n      --red: #d94b2b;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n\n    .ols-revision-page * { box-sizing: border-box; }\n\n    .ols-main {\n      min-width: 0;\n      max-width: 970px;\n    }\n\n    .ols-breadcrumbs {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 8px;\n      margin: 10px 0 22px;\n      font-size: 15px;\n      color: var(--grey-text);\n    }\n\n    .ols-breadcrumbs a,\n    .ols-breadcrumbs span {\n      color: var(--grey-text);\n      text-decoration: none;\n      font-weight: 600;\n    }\n\n    .ols-breadcrumbs a:hover {\n      color: var(--blue);\n      text-decoration: underline;\n      text-underline-offset: 3px;\n    }\n\n    .ols-title-card,\n    .ols-note-card,\n    .ols-h5p-card,\n    .ols-faq-card,\n    .ols-related-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: hidden;\n    }\n\n    .ols-title-card {\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n    }\n\n    .ols-title-card h1 {\n      margin: 0 0 18px;\n      font-size: clamp(36px, 5vw, 58px);\n      line-height: 1.08;\n      font-weight: 800;\n      letter-spacing: -0.04em;\n      color: #111827;\n    }\n\n    .ols-page-intro {\n      font-size: 19px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n      margin: 0 0 22px;\n    }\n\n    .ols-badges {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 12px;\n      margin-bottom: 22px;\n    }\n\n    .ols-badge {\n      display: inline-flex;\n      align-items: center;\n      padding: 9px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      font-size: 15px;\n      font-weight: 600;\n      color: var(--navy);\n    }\n\n    .ols-note-card.soft {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%);\n    }\n\n    .ols-note-card.purple {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%);\n    }\n\n    .ols-note-title {\n      display: flex;\n      align-items: center;\n      gap: 14px;\n      margin-bottom: 20px;\n    }\n\n    .ols-note-icon {\n      width: 52px;\n      height: 52px;\n      border-radius: 16px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-size: 24px;\n      font-weight: 800;\n      flex-shrink: 0;\n    }\n\n    .ols-note-title h2,\n    .ols-h5p-card h2,\n    .ols-faq-card h2,\n    .ols-related-card h2,\n    .ols-infographic-title {\n      margin: 0;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n\n    .ols-h5p-card h2,\n    .ols-faq-card h2,\n    .ols-related-card h2 {\n      margin-bottom: 14px;\n    }\n\n    .ols-note-card p,\n    .ols-note-card li {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-h5p-card p,\n    .ols-faq-card p,\n    .ols-related-card p {\n      font-size: clamp(15px, 1.3vw, 18px);\n      line-height: 1.65;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-note-card strong,\n    .ols-h5p-card strong,\n    .ols-faq-card strong,\n    .ols-related-card strong {\n      font-weight: 700;\n      color: var(--navy);\n    }\n\n    .ols-note-card ul,\n    .ols-note-card ol {\n      margin: 0;\n      padding-left: 22px;\n    }\n\n    .ols-key-box {\n      margin-top: 20px;\n      background: var(--soft-green);\n      border: 1px solid rgba(63, 143, 70, 0.25);\n      border-radius: 20px;\n      padding: 18px 20px;\n    }\n\n    .ols-key-box p {\n      margin: 0;\n      font-weight: 400;\n      color: var(--navy);\n    }\n\n    .ols-definition-box {\n      background: linear-gradient(135deg, #ffffff, var(--soft-purple));\n      border: 2px dashed rgba(122, 62, 157, 0.35);\n      border-radius: 24px;\n      padding: 24px;\n      margin-top: 22px;\n    }\n\n    .ols-definition-box p {\n      margin: 0;\n      color: var(--body-text);\n    }\n\n    .ols-reaction-summary {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-summary-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-summary-item span {\n      display: block;\n      font-size: 13px;\n      font-weight: 700;\n      color: var(--grey-text);\n      margin-bottom: 6px;\n    }\n\n    .ols-summary-item strong {\n      display: block;\n      font-size: 16px;\n      line-height: 1.45;\n      color: var(--navy);\n    }\n\n    .ols-figure-card {\n      margin: 26px 0 4px;\n      border: 1px solid var(--border);\n      border-radius: 26px;\n      overflow: hidden;\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-figure-image {\n      width: 100%;\n      min-height: 260px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      background: #ffffff;\n      padding: 20px;\n    }\n\n    .ols-figure-image img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n      border-radius: 18px;\n    }\n\n    .ols-figure-caption {\n      padding: 18px 22px 20px;\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n    }\n\n    .ols-figure-caption p {\n      margin: 0;\n      color: #5f6b85;\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.6;\n      font-weight: 300;\n      font-style: italic;\n    }\n\n    .ols-table-wrap {\n      overflow: hidden;\n      border-radius: 22px;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      margin-top: 18px;\n    }\n\n    .ols-table {\n      width: 100%;\n      border-collapse: collapse;\n      table-layout: fixed;\n    }\n\n    .ols-table th {\n      background: var(--navy);\n      color: #ffffff;\n      padding: 16px;\n      text-align: left;\n      font-size: clamp(14px, 1.2vw, 17px);\n      font-weight: 600;\n      overflow-wrap: anywhere;\n    }\n\n    .ols-table td {\n      padding: 16px;\n      border-bottom: 1px solid var(--border);\n      font-size: clamp(14px, 1.15vw, 16px);\n      line-height: 1.45;\n      color: var(--body-text);\n      vertical-align: top;\n      overflow-wrap: anywhere;\n    }\n\n    .ols-table tr:last-child td {\n      border-bottom: none;\n    }\n\n    .ols-h5p-card {\n      background: linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%);\n    }\n\n    .ols-h5p-frame {\n      margin-top: 22px;\n      padding: 18px;\n      border-radius: 24px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      box-shadow: inset 0 0 0 1px rgba(28, 36, 75, 0.03);\n    }\n\n    .ols-infographic-full {\n      width: 100%;\n      max-width: 100%;\n      margin: 6px 0 30px;\n      overflow: hidden;\n    }\n\n    .ols-infographic-title {\n      margin: 0 0 18px;\n    }\n\n    .ols-infographic-full-frame {\n      width: 100%;\n      max-width: 100%;\n      border-radius: 22px;\n      overflow: hidden;\n      box-shadow: 0 18px 42px rgba(28, 36, 75, 0.13);\n      background: #ffffff;\n      border: 1px solid var(--border);\n      padding: 24px;\n    }\n\n    .ols-infographic-grid {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 16px;\n    }\n\n    .ols-info-panel {\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      padding: 18px;\n    }\n\n    .ols-info-panel h3 {\n      margin: 0 0 8px;\n      font-size: 21px;\n      line-height: 1.25;\n      color: var(--navy);\n    }\n\n    .ols-info-panel p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.6;\n      color: var(--body-text);\n      font-weight: 300;\n    }\n\n    .ols-faq-list {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n\n    .ols-faq-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px 20px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      line-height: 1.35;\n      color: var(--navy);\n    }\n\n    .ols-faq-item p {\n      margin: 0;\n    }\n\n    .ols-related-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 18px;\n    }\n\n    .ols-related-item {\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 600;\n      line-height: 1.5;\n      transition: transform 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-related-item:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08);\n    }\n\n    .ols-course-cta-topic4,\n    .ols-course-cta-topic4 * {\n      box-sizing: border-box;\n    }\n\n    .ols-course-cta-topic4 {\n      width: 100%;\n      margin: 30px 0 24px;\n      font-family: Poppins, Arial, sans-serif;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-card {\n      overflow: hidden;\n      border-radius: 30px;\n      border: 1px solid var(--border);\n      background:\n        radial-gradient(circle at top left, rgba(37, 99, 235, 0.16), transparent 34%),\n        linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      box-shadow: var(--shadow);\n      padding: 30px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-top {\n      display: grid;\n      grid-template-columns: minmax(260px, 0.9fr) minmax(0, 1.1fr);\n      gap: 28px;\n      align-items: center;\n      margin-bottom: 24px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-image-link {\n      display: block;\n      text-decoration: none;\n      border-radius: 24px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-image {\n      width: 100%;\n      border-radius: 24px;\n      overflow: hidden;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n      transition: transform 0.35s ease, box-shadow 0.35s ease;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-image img {\n      width: 100%;\n      height: auto;\n      display: block;\n      transition: transform 0.45s ease;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-image-link:hover .ols-course-cta-image {\n      transform: translateY(-8px) scale(1.015);\n      box-shadow:\n        0 26px 60px rgba(28, 36, 75, 0.18),\n        0 0 0 1px rgba(37, 99, 235, 0.12);\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-image-link:hover .ols-course-cta-image img {\n      transform: scale(1.03);\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-header-row {\n      display: flex;\n      flex-wrap: wrap;\n      align-items: center;\n      justify-content: space-between;\n      gap: 14px;\n      margin-bottom: 18px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-kicker {\n      display: inline-flex;\n      align-items: center;\n      padding: 8px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      color: var(--blue);\n      font-size: 14px;\n      line-height: 1.2;\n      font-weight: 700;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-course-cta-topic4 h2 {\n      margin: 0 0 14px;\n      font-size: clamp(28px, 3.5vw, 42px);\n      line-height: 1.15;\n      font-weight: 800;\n      letter-spacing: -0.03em;\n      color: #111827;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-intro-stats {\n      display: grid;\n      grid-template-columns: minmax(0, 1.08fr) minmax(320px, 0.92fr);\n      gap: 24px;\n      align-items: stretch;\n      margin: 0 0 30px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-intro {\n      margin: 0;\n      color: var(--body-text);\n      font-size: clamp(16px, 1.4vw, 18px);\n      line-height: 1.7;\n      font-weight: 300;\n      align-self: center;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-stats {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin: 0;\n    }\n\n    .ols-course-cta-topic4 .ols-course-stat {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-course-cta-topic4 .ols-course-stat span {\n      display: block;\n      margin-bottom: 6px;\n      color: var(--grey-text);\n      font-size: 13px;\n      line-height: 1.35;\n      font-weight: 700;\n    }\n\n    .ols-course-cta-topic4 .ols-course-stat strong {\n      display: block;\n      color: var(--navy);\n      font-size: 18px;\n      line-height: 1.35;\n      font-weight: 800;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-features {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin: 0 0 30px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-feature {\n      background: rgba(255, 255, 255, 0.78);\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 16px 18px;\n    }\n\n    .ols-course-cta-topic4 .ols-course-feature h3 {\n      margin: 0 0 6px;\n      color: var(--navy);\n      font-size: 18px;\n      line-height: 1.3;\n      font-weight: 800;\n    }\n\n    .ols-course-cta-topic4 .ols-course-feature p {\n      margin: 0;\n      color: var(--body-text);\n      font-size: 15px;\n      line-height: 1.6;\n      font-weight: 300;\n    }\n\n    .ols-course-cta-topic4 .ols-course-cta-bottom {\n      display: flex;\n      justify-content: center;\n      padding-top: 22px;\n      border-top: 1px solid var(--border);\n    }\n\n    .ols-course-cta-topic4 .ols-course-button {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      padding: 15px 28px;\n      border-radius: 999px;\n      background: var(--navy);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 16px;\n      line-height: 1.2;\n      font-weight: 800;\n      box-shadow: 0 12px 26px rgba(28, 36, 75, 0.18);\n      transition: transform 0.2s ease, background 0.2s ease, box-shadow 0.2s ease;\n    }\n\n    .ols-course-cta-topic4 .ols-course-button:hover {\n      transform: translateY(-2px);\n      background: var(--blue);\n      color: #ffffff;\n      box-shadow: 0 16px 32px rgba(37, 99, 235, 0.24);\n    }\n\n    .ols-course-cta-topic4 .ols-course-button-top {\n      flex-shrink: 0;\n      padding: 12px 22px;\n      font-size: 15px;\n    }\n\n    @media (max-width: 1050px) {\n\n      .ols-main {\n        max-width: none;\n      }\n\n      .ols-related-grid,\n      .ols-infographic-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n\n      .ols-course-cta-topic4 .ols-course-cta-top,\n      .ols-course-cta-topic4 .ols-course-cta-intro-stats {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-course-cta-topic4 .ols-course-cta-image-link {\n        max-width: 520px;\n        margin: 0 auto;\n      }\n    }\n\n    @media (max-width: 760px) {\n\n      .ols-title-card,\n      .ols-note-card,\n      .ols-h5p-card,\n      .ols-faq-card,\n      .ols-related-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-note-title {\n        align-items: flex-start;\n      }\n\n      .ols-figure-card {\n        border-radius: 22px;\n      }\n\n      .ols-figure-image {\n        min-height: 210px;\n        padding: 14px;\n      }\n\n      .ols-figure-caption {\n        padding: 18px;\n      }\n\n      .ols-infographic-full {\n        margin: 0 0 26px;\n      }\n\n      .ols-infographic-full-frame {\n        border-radius: 18px;\n        padding: 18px;\n      }\n\n      .ols-table thead {\n        display: none;\n      }\n\n      .ols-table,\n      .ols-table tbody,\n      .ols-table tr,\n      .ols-table td {\n        display: block;\n        width: 100%;\n      }\n\n      .ols-table tr {\n        border-bottom: 1px solid var(--border);\n        padding: 12px 0;\n      }\n\n      .ols-table tr:last-child {\n        border-bottom: none;\n      }\n\n      .ols-table td {\n        border-bottom: none;\n        padding: 10px 14px;\n      }\n\n      .ols-table td::before {\n        content: attr(data-label);\n        display: block;\n        margin-bottom: 5px;\n        color: var(--navy);\n        font-weight: 800;\n      }\n\n      .ols-course-cta-topic4 {\n        margin: 26px 0 22px;\n      }\n\n      .ols-course-cta-topic4 .ols-course-cta-card {\n        padding: 20px;\n        border-radius: 24px;\n      }\n\n      .ols-course-cta-topic4 .ols-course-cta-header-row {\n        align-items: stretch;\n      }\n\n      .ols-course-cta-topic4 .ols-course-button-top {\n        width: 100%;\n      }\n\n      .ols-course-cta-topic4 .ols-course-cta-stats,\n      .ols-course-cta-topic4 .ols-course-cta-features {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-course-cta-topic4 .ols-course-button {\n        width: 100%;\n      }\n    }\n\n    \/* OLS saved author profile block *\/\n    .ols-author{\n        display:flex;\n        align-items:center;\n        gap:20px;\n        padding:28px;\n        border-radius:28px;\n        background:linear-gradient(135deg,#ffffff 0%,#f8fbff 100%);\n        border:1px solid rgba(28,36,75,0.12);\n        box-shadow:0 18px 45px rgba(28,36,75,0.10);\n      }\n    \n      .ols-author-avatar-img{\n        width:92px;\n        height:92px;\n        border-radius:50%;\n        object-fit:cover;\n        object-position:center;\n        flex-shrink:0;\n        border:4px solid #ffffff;\n        box-shadow:\n          0 14px 32px rgba(28,36,75,0.18),\n          0 0 0 1px rgba(28,36,75,0.10);\n        transition:\n          transform 0.25s ease,\n          box-shadow 0.25s ease;\n      }\n    \n      .ols-author:hover .ols-author-avatar-img{\n        transform:scale(1.04);\n        box-shadow:\n          0 20px 42px rgba(28,36,75,0.22),\n          0 0 0 1px rgba(28,36,75,0.10);\n      }\n    \n      .ols-author-content{\n        min-width:0;\n      }\n    \n      .ols-author-title{\n        margin:0 0 4px;\n        font-size:clamp(24px,3vw,34px);\n        line-height:1.15;\n        font-weight:700;\n        color:#1C244B;\n        letter-spacing:-0.03em;\n      }\n    \n      .ols-author-description{\n        margin:0;\n        font-size:17px;\n        line-height:1.7;\n        font-weight:300;\n        color:#667085;\n      }\n    \n      .ols-linkedin-pill{\n        display:inline-flex;\n        align-items:center;\n        justify-content:center;\n        gap:10px;\n        margin-top:16px;\n        padding:11px 18px;\n        border-radius:999px;\n        background:linear-gradient(135deg,#0A66C2,#004182);\n        color:#ffffff !important;\n        text-decoration:none;\n        font-size:14px;\n        line-height:1;\n        font-weight:700;\n        letter-spacing:0.01em;\n        box-shadow:0 10px 22px rgba(10,102,194,0.24);\n        position:relative;\n        overflow:hidden;\n        transition:\n          transform 0.22s ease,\n          box-shadow 0.22s ease;\n      }\n    \n      .ols-linkedin-pill::before{\n        content:\"\";\n        position:absolute;\n        top:0;\n        left:-120%;\n        width:100%;\n        height:100%;\n        background:linear-gradient(\n          120deg,\n          rgba(255,255,255,0) 0%,\n          rgba(255,255,255,0.28) 50%,\n          rgba(255,255,255,0) 100%\n        );\n        transition:left 0.7s ease;\n      }\n    \n      .ols-linkedin-pill:hover{\n        color:#ffffff !important;\n        transform:translateY(-3px) scale(1.03);\n        box-shadow:\n          0 16px 34px rgba(10,102,194,0.34),\n          0 0 0 6px rgba(10,102,194,0.10);\n      }\n    \n      .ols-linkedin-pill:hover::before{\n        left:120%;\n      }\n    \n      .ols-linkedin-icon{\n        width:18px;\n        height:18px;\n        display:block;\n        flex-shrink:0;\n      }\n    \n      @media (max-width:640px){\n    \n        .ols-author{\n          align-items:flex-start;\n          padding:22px 18px;\n          border-radius:22px;\n        }\n    \n        .ols-author-avatar-img{\n          width:72px;\n          height:72px;\n        }\n    \n        .ols-author-title{\n          font-size:24px;\n        }\n    \n        .ols-author-description{\n          font-size:15px;\n        }\n      }\n    \n      .ols-linkedin-pill:hover, .ols-linkedin-pill:focus { color:#ffffff !important; }\n    \n    .ols-figure-placeholder .ols-placeholder-box { border: 2px dashed #c9973a; background: #fffaf0; border-radius: 16px; padding: 26px 22px; font-weight: 700; color: #7a4b12; text-align: center; line-height: 1.6; }\n    .ols-figure-placeholder .ols-figure-image { background: transparent; }\n    .ols-figure-placeholder { background: #ffffff; border: 1px solid rgba(28, 36, 75, 0.12); border-radius: 22px; padding: 14px; margin: 18px 0 6px; }\n    .ols-figure-placeholder .ols-figure-caption p { margin: 10px 0 0; font-size: 14px; color: #667085; text-align: center; }\n<\/style>\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>AQA A Level Chemistry<\/p>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>3.3.2 Alkanes<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/\">Section overview<\/a><\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/crude-oil\/cracking\/\">Cracking<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/crude-oil\/reforming\/\">Reforming<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/crude-oil\/thermal-and-catalytic-cracking\/\">Thermal and Catalytic Cracking<\/a><\/li>\n        <\/ul>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/\">Alkanes as Fuel<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/combustion\/\">Combustion<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/\">Flue-Gas Desulfurisation<\/a><\/li>\n        <\/ul>\n      <\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/alternative-fuel\/\">Alternative Fuel<\/a><\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/\">Reactions of Alkanes<\/a>\n        <ul class=\"ols-subtopic-list\">\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/initiation\/\">Initiation<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/propagation\/\">Propagation<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/termination\/\">Termination<\/a><\/li>\n          <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a><\/li>\n        <\/ul>\n      <\/li>\n    <\/ul>\n  <\/div>\n  <div class=\"ols-topic-group\">\n    <h4>Other AQA Sections<\/h4>\n    <ul class=\"ols-topic-list\">\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-1-introduction-to-organic-chemistry\/\">3.3.1 Introduction to Organic Chemistry<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-4-alkenes\/\">3.3.4 Alkenes<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-1-atomicstructure\/\">3.1.1 Atomic Structure<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-2-amount-of-substance\/\">3.1.2 Amount of Substance<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-1-3-bonding\/\">3.1.3 Bonding<\/a><\/li>\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-2-1-periodicity\/\">3.2.1 Periodicity<\/a><\/li>\n    <\/ul>\n  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highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/\">AQA<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/\">3.3.2 Alkanes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/\">Alkanes as Fuel<\/a> \/\n<span>Flue-Gas Desulfurisation<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Flue-Gas Desulfurisation<\/h1>\n        <p class=\"ols-page-intro\">A concise AQA A Level Chemistry revision guide to removing sulfur dioxide from the flue gases of power stations using calcium oxide or calcium carbonate: the equations, why an acidic gas reacts with a basic solid, and what happens to the products (3.3.2.3).<\/p>\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Paper 2<\/div>\n<div class=\"ols-badge\">AQA<\/div>\n<div class=\"ols-badge\">3.3.2 Alkanes<\/div>\n<div class=\"ols-badge\">7405\/2<\/div>\n        <\/div>\n\n        <div class=\"ols-author\">\n        \n            <img decoding=\"async\"\n              class=\"ols-author-avatar-img\"\n              src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\"\n              alt=\"Dr. Mohammed Al-Fatah\"\n            >\n        \n            <div class=\"ols-author-content\">\n        \n              <h2 class=\"ols-author-title\">\n                Written by: Dr. Mohammed Al-Fatah\n              <\/h2>\n        \n              <p class=\"ols-author-description\">\n                Chemistry specialist revision notes for A Level Chemistry.\n              <\/p>\n        \n              <a class=\"ols-linkedin-pill\" href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\" target=\"_blank\" rel=\"noopener noreferrer\">\n        \n                <svg class=\"ols-linkedin-icon\" viewBox=\"0 0 24 24\" fill=\"currentColor\" aria-hidden=\"true\">\n                  <path d=\"M4.98 3.5C4.98 4.88 3.86 6 2.48 6S0 4.88 0 3.5 1.12 1 2.48 1s2.5 1.12 2.5 2.5zM.5 8h4V24h-4V8zm7 0h3.8v2.2h.1c.5-.9 1.8-2.2 3.9-2.2 4.2 0 5 2.8 5 6.4V24h-4v-7.6c0-1.8 0-4.2-2.6-4.2s-3 2-3 4v7.8h-4V8z\"\/>\n                <\/svg>\n        \n                View LinkedIn Profile\n        \n              <\/a>\n        \n            <\/div>\n        \n          <\/div>\n      <\/header>\n\n      <section class=\"ols-h5p-card ols-h5p-inline ols-h5p-recap\">\n<span class=\"ols-h5p-kicker\">Before you start<\/span>\n<h2>GCSE Recap: From Limestone to Quicklime<\/h2>\n<p>Before you start, check where quicklime comes from, why it costs more than limestone, and what a base does to an acid.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"815\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>Why Sulfur Dioxide Has to Be Removed<\/h2>\n<\/div>\n<p>Coal and some crude-oil fractions contain <strong>sulfur compounds<\/strong>. When the fuel burns in a power station the sulfur is oxidised to <strong>sulfur dioxide<\/strong>, SO<sub>2<\/sub>, which leaves in the <strong>flue gases<\/strong>, the waste gases that go up the chimney (the flue). Sulfur dioxide dissolves in water in the atmosphere to form sulfurous acid, and is oxidised to sulfuric acid, giving <strong>acid rain<\/strong>.<\/p>\n<p>AQA 3.3.2.3 asks you to <strong>explain why sulfur dioxide can be removed from flue gases using calcium oxide or calcium carbonate<\/strong>. The key idea is an acid-base reaction: sulfur dioxide is an <strong>acidic oxide<\/strong>, and calcium oxide and calcium carbonate are <strong>basic<\/strong>, so they neutralise it.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Sulfur dioxide is an acidic, non-metal oxide. Calcium oxide (a basic metal oxide) and calcium carbonate (a carbonate) both react with acids, so they react with sulfur dioxide and remove it from the gas stream.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: A Ship&#039;s Exhaust Scrubber<\/h2>\n<p>Apply the acid-base idea to a scrubber that uses no calcium compound at all.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-390\" class=\"h5p-iframe\" data-content-id=\"390\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Flue-Gas Desulfurisation MCQ: Scrubbing a Ship&#039;s Exhaust with Seawater\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>Removal with Calcium Oxide<\/h2>\n<\/div>\n<p>Calcium oxide, <strong>lime<\/strong>, reacts directly with sulfur dioxide to form calcium sulfite (calcium sulfate(IV)):<\/p>\n<p style=\"text-align:center\"><strong>CaO(s) + SO<sub>2<\/sub>(g) &rarr; CaSO<sub>3<\/sub>(s)<\/strong><\/p>\n<p>This is a neutralisation: the basic oxide and the acidic oxide combine to form a salt. In practice the calcium oxide is mixed with water to make a slurry of calcium hydroxide, which is sprayed into the flue gases in a <strong>scrubber<\/strong>. The calcium sulfite is then oxidised by air to <strong>calcium sulfate<\/strong>:<\/p>\n<p style=\"text-align:center\"><strong>2CaSO<sub>3<\/sub>(s) + O<sub>2<\/sub>(g) &rarr; 2CaSO<sub>4<\/sub>(s)<\/strong><\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Calcium oxide is a basic oxide, so it neutralises the acidic sulfur dioxide, forming calcium sulfite which is oxidised to calcium sulfate.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Equations for Other Bases<\/h2>\n<p>Work each equation and each number out on paper, then type your answer in.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-389\" class=\"h5p-iframe\" data-content-id=\"389\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Flue-Gas Desulfurisation Blanks: Other Bases That Trap Sulfur Dioxide\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Removal with Calcium Carbonate<\/h2>\n<\/div>\n<p>Calcium carbonate, <strong>limestone<\/strong>, is cheaper than lime and works in the same way, but carbon dioxide is released as well:<\/p>\n<p style=\"text-align:center\"><strong>CaCO<sub>3<\/sub>(s) + SO<sub>2<\/sub>(g) &rarr; CaSO<sub>3<\/sub>(s) + CO<sub>2<\/sub>(g)<\/strong><\/p>\n<p>Again the calcium sulfite is oxidised to calcium sulfate in the scrubber. Powdered limestone in water is the most common desulfurisation method in coal-fired power stations because limestone is abundant and inexpensive.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th><\/th><th>Calcium oxide (lime)<\/th><th>Calcium carbonate (limestone)<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Equation with SO<sub>2<\/sub><\/strong><\/td><td>CaO + SO<sub>2<\/sub> &rarr; CaSO<sub>3<\/sub><\/td><td>CaCO<sub>3<\/sub> + SO<sub>2<\/sub> &rarr; CaSO<sub>3<\/sub> + CO<sub>2<\/sub><\/td><\/tr>\n<tr><td><strong>Type of reaction<\/strong><\/td><td>Acidic oxide + basic oxide (neutralisation)<\/td><td>Acidic oxide + carbonate (neutralisation)<\/td><\/tr>\n<tr><td><strong>Gas released<\/strong><\/td><td>None<\/td><td>Carbon dioxide, a greenhouse gas<\/td><\/tr>\n<tr><td><strong>Cost<\/strong><\/td><td>Higher: lime is made by heating limestone<\/td><td>Lower: limestone is quarried and ground<\/td><\/tr>\n<tr><td><strong>Final product after oxidation<\/strong><\/td><td>Calcium sulfate (gypsum)<\/td><td>Calcium sulfate (gypsum)<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"ols-figure-card ols-zoom-pop\">\n<div class=\"ols-figure-image\">\n<a class=\"ols-image-fullscreen-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/schematic-of-a-wet-flue-gas-desulfurisation-scrubber.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/schematic-of-a-wet-flue-gas-desulfurisation-scrubber.jpg\" alt=\"Wet flue-gas desulfurisation scrubber using limestone slurry to remove sulfur dioxide and produce gypsum\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/schematic-of-a-wet-flue-gas-desulfurisation-scrubber.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>A wet scrubber: limestone slurry neutralises the sulfur dioxide, and air oxidises the calcium sulfite to calcium sulfate, sold as gypsum.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> If asked for a disadvantage of using calcium carbonate, say that carbon dioxide is released, which contributes to global warming. If asked for an advantage, say it is cheaper and more abundant than calcium oxide.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Lime or Limestone?<\/h2>\n<p>In each round, choose the one statement that is accurate for the boiler house described.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-391\" class=\"h5p-iframe\" data-content-id=\"391\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Flue-Gas Desulfurisation Summary: Four Decisions at a Boiler House\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>What Happens to the Calcium Sulfate<\/h2>\n<\/div>\n<p>Flue-gas desulfurisation produces large amounts of <strong>calcium sulfate<\/strong>. Hydrated calcium sulfate is <strong>gypsum<\/strong>, CaSO<sub>4<\/sub>&middot;2H<sub>2<\/sub>O, which is used to make <strong>plasterboard<\/strong> and cement. Selling the gypsum offsets part of the cost of the process, so the sulfur is turned from a pollutant into a useful product.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Stage<\/th><th>Species<\/th><th>Role<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Before scrubbing<\/strong><\/td><td>SO<sub>2<\/sub><\/td><td>Acidic pollutant that would cause acid rain<\/td><\/tr>\n<tr><td><strong>Neutralisation<\/strong><\/td><td>CaSO<sub>3<\/sub><\/td><td>Calcium sulfite formed from CaO or CaCO<sub>3<\/sub><\/td><\/tr>\n<tr><td><strong>Oxidation with air<\/strong><\/td><td>CaSO<sub>4<\/sub><\/td><td>Calcium sulfate, hydrated to gypsum<\/td><\/tr>\n<tr><td><strong>Use<\/strong><\/td><td>CaSO<sub>4<\/sub>&middot;2H<sub>2<\/sub>O<\/td><td>Plasterboard and cement<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> The process removes about 90 per cent of the sulfur dioxide from the flue gases and produces gypsum that can be sold.<\/p>\n<\/div>\n<\/article>\n<section class=\"ols-h5p-card ols-h5p-inline\">\n<span class=\"ols-h5p-kicker\">Check your understanding<\/span>\n<h2>Quick Check: Explain the Rejected Delivery<\/h2>\n<p>Write a short explanation, then compare it with the mark points and the model answer.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-816\" class=\"h5p-iframe\" data-content-id=\"816\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Flue-Gas Desulfurisation Explain: The Rejected Load of Scrubber Solid\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card purple\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>Common Exam Mistakes<\/h2>\n<\/div>\n<ul>\n<li>Describing the reaction as combustion or oxidation. The removal step is a <strong>neutralisation<\/strong>: acidic SO<sub>2<\/sub> reacts with basic CaO or CaCO<sub>3<\/sub>.<\/li>\n<li>Writing calcium sulfate, CaSO<sub>4<\/sub>, as the direct product of the reaction with SO<sub>2<\/sub>. The first product is calcium <strong>sulfite<\/strong>, CaSO<sub>3<\/sub>; sulfate forms only after oxidation by air.<\/li>\n<li>Forgetting the carbon dioxide in the calcium carbonate equation, so the equation does not balance.<\/li>\n<li>Confusing flue-gas desulfurisation with the catalytic converter, which removes CO, NO<sub>x<\/sub> and unburned hydrocarbons from vehicle exhausts, not SO<sub>2<\/sub> from power stations.<\/li>\n<\/ul>\n<div class=\"ols-key-box\">\n<p><strong>Exam sentence:<\/strong> Sulfur dioxide is an acidic gas, so it is removed from flue gases by reaction with the base calcium oxide or with calcium carbonate, forming calcium sulfite and then calcium sulfate.<\/p>\n<\/div>\n<\/article>\n\n<section class=\"ols-course-cta-alkenes\" id=\"olsCourseCtaAlkenes001\">\r\n  <style>\r\n    .ols-course-cta-alkenes,\r\n    .ols-course-cta-alkenes * {\r\n      box-sizing: border-box;\r\n    }\r\n\r\n    .ols-course-cta-alkenes {\r\n      --navy: #1C244B;\r\n      --blue: 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src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/aqa-a-level-chemistry-3-3-1-3-3-2-organic-chemistry-alkanes-interactive-course-banner.jpg\"\r\n            alt=\"AQA A Level Chemistry 3.3.4 Introduction to Organic Chemistry and Alkanes interactive course banner\"\r\n          >\r\n        <\/div>\r\n\r\n      <\/a>\r\n\r\n      <div class=\"ols-course-cta-content\">\r\n\r\n        <div class=\"ols-course-cta-header-row\">\r\n\r\n          <div class=\"ols-course-cta-kicker\">\r\n            AQA 7405 | 3.3.1 and 3.3.2 Course\r\n          <\/div>\r\n\r\n          <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/introduction-to-organic-chemistry-and-alkanes-3-3-1-3-3-2-aqa\/\">\r\n            View Course\r\n          <\/a>\r\n\r\n        <\/div>\r\n\r\n        <h2>\r\n          Master Introduction to Organic Chemistry and Alkanes for AQA A Level Chemistry\r\n        <\/h2>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-intro-stats\">\r\n\r\n      <p class=\"ols-course-cta-intro\">\r\n        Continue from these free revision notes into the full 3.3.1 and 3.3.2 Introduction to Organic Chemistry and Alkanes course. The six guided video lessons are ready now; the AQA MCQ bank, teacher-marked short-answer questions, supplementary lessons and KASP spec-point report are being written, and the course opens for enrolment as soon as they are complete.\r\n      <\/p>\r\n\r\n      <div class=\"ols-course-cta-stats\">\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Recorded lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>Video lessons<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>MCQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n        <div class=\"ols-course-stat\">\r\n          <span>SAQ practice<\/span>\n          <strong>Coming soon<\/strong>\r\n        <\/div>\r\n\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-features\">\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Guided video teaching<\/h3>\r\n        <p>\r\n          Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Instant MCQ feedback<\/h3>\r\n        <p>\r\n          Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Teacher-marked SAQs<\/h3>\r\n        <p>\r\n          Submit written exam responses and receive chemistry specialist feedback with improvement guidance.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"ols-course-feature\">\r\n        <h3>Progress tracking<\/h3>\r\n        <p>\r\n          Identify strengths and weaknesses across the full 3.3.1 and 3.3.2 specification with targeted reporting.\r\n        <\/p>\r\n      <\/div>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-animation-wrap\">\r\n\r\n      <h3 class=\"ols-course-animation-title\">\r\n        See how the course works\r\n      <\/h3>\r\n\r\n      <div class=\"ols-animation-frame-shell\">\r\n        <iframe\r\n          id=\"olsCourseAnimationFrame001\"\r\n          title=\"OLS course preview animation\"\r\n          loading=\"lazy\"\r\n          referrerpolicy=\"no-referrer\">\r\n        <\/iframe>\r\n\r\n        <button\r\n          class=\"ols-animation-start-overlay\"\r\n          id=\"olsCourseAnimationStart001\"\r\n          type=\"button\"\r\n          aria-label=\"Play OLS course preview animation\">\r\n          <span class=\"ols-animation-start-content\">\r\n            <span class=\"ols-animation-play-circle\" aria-hidden=\"true\">\r\n              <span class=\"ols-animation-play-icon\"><\/span>\r\n            <\/span>\r\n            <span class=\"ols-animation-start-text\">\r\n              Play course preview animation\r\n            <\/span>\r\n          <\/span>\r\n        <\/button>\r\n\r\n        <button\r\n          class=\"ols-animation-pause-button\"\r\n          id=\"olsCourseAnimationPause001\"\r\n          type=\"button\"\r\n          aria-label=\"Pause course preview animation\">\r\n          Pause\r\n        <\/button>\r\n      <\/div>\r\n\r\n      <p class=\"ols-course-video-status\">\r\n        Click play to start the course preview animation.\r\n      <\/p>\r\n\r\n    <\/div>\r\n\r\n    <div class=\"ols-course-cta-bottom\">\r\n\r\n      <a class=\"ols-course-button\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/introduction-to-organic-chemistry-and-alkanes-3-3-1-3-3-2-aqa\/\">\r\n        View Introduction to Organic Chemistry and Alkanes Course\r\n      <\/a>\r\n\r\n    <\/div>\r\n\r\n  <\/div>\r\n\r\n  <template id=\"olsCourseAnimationTemplate001\">\r\n<!DOCTYPE html>\r\n<html lang=\"en\">\r\n<head>\r\n<meta charset=\"UTF-8\">\r\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\r\n<title>OLS Combined Promo Animation<\/title>\r\n\r\n<style>\r\n*{box-sizing:border-box;}\r\n\r\nhtml.ols-animation-paused *,\r\nhtml.ols-animation-paused *::before,\r\nhtml.ols-animation-paused *::after{\r\n  animation-play-state:paused!important;\r\n}\r\n\r\n:root{\r\n  --ols-video-screen-w:1180;\r\n  --ols-video-screen-h:664;\r\n  --ols-video-screen-scale:1;\r\n  --ols-mcq-screen-w:1360;\r\n  --ols-mcq-screen-h:1130;\r\n  --ols-mcq-screen-scale:1;\r\n  --ols-saq-screen-w:1360;\r\n  --ols-saq-screen-h:965;\r\n  --ols-saq-screen-scale:1;\r\n}\r\n\r\nhtml,\r\nbody{\r\n  width:100%;\r\n  height:100%;\r\n}\r\n\r\nbody{\r\n  margin:0;\r\n  overflow:hidden;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  background:#e9efff;\r\n}\r\n\r\n.ols-combined-stage{\r\n  position:relative;\r\n  width:100vw;\r\n  height:100vh;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-scene{\r\n  position:absolute;\r\n  inset:0;\r\n  width:100vw;\r\n  height:100vh;\r\n  opacity:0;\r\n  visibility:hidden;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-scene.active{\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:auto;\r\n}\r\n\r\n.ols-scene.fade-out{\r\n  animation:olsSceneFadeOut 0.85s ease forwards;\r\n}\r\n\r\n@keyframes olsSceneFadeOut{\r\n  to{\r\n    opacity:0;\r\n    visibility:hidden;\r\n  }\r\n}\r\n\r\n.ols-title-cursor{\r\n  display:inline-block;\r\n  width:5px;\r\n  height:0.85em;\r\n  background:#1C244B;\r\n  margin-left:8px;\r\n  transform:translateY(8px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n.cursor{\r\n  display:inline-block;\r\n  width:3px;\r\n  height:28px;\r\n  background:#1c244b;\r\n  margin-left:3px;\r\n  transform:translateY(5px);\r\n  animation:olsBlink 0.8s infinite;\r\n}\r\n\r\n@keyframes olsBlink{\r\n  0%,45%{opacity:1;}\r\n  46%,100%{opacity:0;}\r\n}\r\n\r\n.ols-video-stage,\r\n.ols-mcq-stage,\r\n.ols-saq-stage{\r\n  width:100vw;\r\n  height:100vh;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  padding:0;\r\n  overflow:hidden;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n}\r\n\r\n.ols-video-title-screen,\r\n.ols-mcq-intro-screen,\r\n.ols-saq-intro{\r\n  position:absolute;\r\n  inset:0;\r\n  z-index:50;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  background:\r\n    radial-gradient(circle at top left,rgba(70,127,247,0.14),transparent 34%),\r\n    linear-gradient(135deg,#f8fbff 0%,#e9efff 100%);\r\n  opacity:1;\r\n  visibility:visible;\r\n  pointer-events:none;\r\n}\r\n\r\n.ols-video-title-screen.hide{animation:olsVideoTitleFadeOut 0.85s ease forwards;}\r\n.ols-mcq-intro-screen.hide{animation:olsMcqIntroFadeOut 0.85s ease forwards;}\r\n.ols-saq-intro.hide{animation:olsSaqIntroFadeOut 0.85s ease forwards;}\r\n\r\n@keyframes olsVideoTitleFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsMcqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n@keyframes olsSaqIntroFadeOut{to{opacity:0;visibility:hidden;}}\r\n\r\n.ols-video-title-wrap,\r\n.ols-mcq-intro-title-wrap,\r\n.ols-saq-intro-title-wrap{\r\n  max-width:1250px;\r\n  padding:0 34px;\r\n  text-align:center;\r\n}\r\n\r\n.ols-video-title,\r\n.ols-mcq-intro-title,\r\n.ols-saq-intro-title{\r\n  margin:0;\r\n  font-family:Poppins,Arial,sans-serif;\r\n  font-size:clamp(52px,8vw,124px);\r\n  font-weight:600;\r\n  line-height:1.08;\r\n  color:#1C244B;\r\n  text-shadow:-9px 0 9px rgba(28,36,75,0.16);\r\n  letter-spacing:-0.045em;\r\n}\r\n\r\n#videoTitleText,\r\n#mcqIntroTitleText,\r\n#saqIntroTitleText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.ols-video-scene{\r\n  width:100%;\r\n  height:100%;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  opacity:0;\r\n  visibility:hidden;\r\n}\r\n\r\n.ols-video-scene.show{\r\n  visibility:visible;\r\n  animation:olsVideoSceneIn 1s ease forwards;\r\n}\r\n\r\n@keyframes olsVideoSceneIn{to{opacity:1;}}\r\n\r\n.ols-video-scale-wrap{\r\n  width:calc(var(--ols-video-screen-w) * 1px);\r\n  height:calc(var(--ols-video-screen-h) * 1px);\r\n  transform:scale(var(--ols-video-screen-scale));\r\n  transform-origin:center center;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n}\r\n\r\n.ols-video-card{\r\n  width:1180px;\r\n  height:664px;\r\n  border-radius:28px;\r\n  overflow:hidden;\r\n  background:#1C244B;\r\n  box-shadow:0 28px 80px rgba(28,36,75,0.28);\r\n  transform:translateY(24px) scale(0.96);\r\n  opacity:0;\r\n}\r\n\r\n.ols-video-scene.show .ols-video-card{\r\n  animation:olsVideoCardIn 1s cubic-bezier(.18,.89,.32,1.12) forwards;\r\n  animation-delay:0.2s;\r\n}\r\n\r\n@keyframes olsVideoCardIn{\r\n  to{\r\n    transform:translateY(0) scale(1);\r\n    opacity:1;\r\n  }\r\n}\r\n\r\n.ols-video-card video{\r\n  display:block;\r\n  width:100%;\r\n  height:100%;\r\n  aspect-ratio:16 \/ 9;\r\n  object-fit:cover;\r\n  border:0;\r\n}\r\n\r\n.ols-mcq-scale-wrap,\r\n.ols-saq-scale-wrap{\r\n  width:calc(var(--ols-mcq-screen-w) * 1px);\r\n  height:calc(var(--ols-mcq-screen-h) * 1px);\r\n  transform:scale(var(--ols-mcq-screen-scale));\r\n  transform-origin:center center;\r\n  display:flex;\r\n  justify-content:center;\r\n  align-items:flex-start;\r\n}\r\n\r\n.ols-saq-scale-wrap{\r\n  width:calc(var(--ols-saq-screen-w) * 1px);\r\n  height:calc(var(--ols-saq-screen-h) * 1px);\r\n  transform:scale(var(--ols-saq-screen-scale));\r\n}\r\n\r\n.ols-mcq-screen{\r\n  width:1360px;\r\n  height:1130px;\r\n  border-radius:22px;\r\n  overflow:hidden;\r\n  background:#eaf0ff;\r\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\r\n  opacity:0;\r\n  transform:translateY(24px) scale(0.96);\r\n}\r\n\r\n.ols-mcq-screen.show{\r\n  animation:olsMcqScreenEnter 1s ease forwards;\r\n}\r\n\r\n@keyframes olsMcqScreenEnter{\r\n  from{opacity:0;transform:translateY(24px) scale(0.96);}\r\n  to{opacity:1;transform:translateY(0) scale(1);}\r\n}\r\n\r\n.mcq-question-area{\r\n  background:#eaf0ff;\r\n  padding:28px 30px 30px;\r\n  position:relative;\r\n  height:610px;\r\n}\r\n\r\n.mcq-question-lead{\r\n  margin:0 0 14px;\r\n  font-size:24px;\r\n  line-height:1.35;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-ionic-table{\r\n  border-collapse:collapse;\r\n  width:500px;\r\n  margin-bottom:8px;\r\n  font-size:21px;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-ionic-table th,\r\n.mcq-ionic-table td{\r\n  border:1.5px solid #c9ced8;\r\n  padding:12px 18px;\r\n  text-align:center;\r\n}\r\n\r\n.mcq-ionic-table th{\r\n  background:#f2f2f2;\r\n  font-weight:700;\r\n}\r\n\r\n.mcq-ionic-table td{\r\n  background:#eaf0ff;\r\n}\r\n\r\n.mcq-question-main{\r\n  margin:6px 0 28px;\r\n  font-size:24px;\r\n  line-height:1.35;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-options-wrap{\r\n  display:flex;\r\n  flex-direction:column;\r\n  gap:17px;\r\n  max-width:1200px;\r\n}\r\n\r\n.mcq-option-row{\r\n  display:flex;\r\n  align-items:center;\r\n  min-height:34px;\r\n  position:relative;\r\n}\r\n\r\n.mcq-radio{\r\n  width:28px;\r\n  height:28px;\r\n  border-radius:50%;\r\n  border:2px solid #6b7280;\r\n  margin-right:16px;\r\n  background:transparent;\r\n  position:relative;\r\n  flex:0 0 auto;\r\n}\r\n\r\n.mcq-radio::after{\r\n  content:\"\";\r\n  position:absolute;\r\n  inset:5px;\r\n  border-radius:50%;\r\n  background:#6b7280;\r\n  opacity:0;\r\n  transform:scale(0.4);\r\n  transition:opacity 0.25s ease,transform 0.25s ease;\r\n}\r\n\r\n.mcq-option-row.selected .mcq-radio::after{\r\n  opacity:1;\r\n  transform:scale(1);\r\n}\r\n\r\n.mcq-radio-ripple{\r\n  position:absolute;\r\n  left:14px;\r\n  top:50%;\r\n  width:28px;\r\n  height:28px;\r\n  border-radius:50%;\r\n  border:2px solid rgba(28,36,75,0.28);\r\n  transform:translate(-50%,-50%) scale(1);\r\n  opacity:0;\r\n  pointer-events:none;\r\n}\r\n\r\n.mcq-option-row.clicking .mcq-radio-ripple{\r\n  animation:mcqRipple 0.75s ease forwards;\r\n}\r\n\r\n@keyframes mcqRipple{\r\n  0%{opacity:0.65;transform:translate(-50%,-50%) scale(1);}\r\n  100%{opacity:0;transform:translate(-50%,-50%) scale(2.5);}\r\n}\r\n\r\n.mcq-option-label{\r\n  font-size:23px;\r\n  color:#111827;\r\n}\r\n\r\n.mcq-specific-feedback{\r\n  display:inline-flex;\r\n  align-items:center;\r\n  margin-left:18px;\r\n  min-height:38px;\r\n  opacity:0;\r\n  transform:translateX(-8px);\r\n}\r\n\r\n.mcq-specific-feedback.show{\r\n  opacity:1;\r\n  transform:translateX(0);\r\n  transition:opacity 0.35s ease,transform 0.35s ease;\r\n}\r\n\r\n.mcq-cross-icon{\r\n  width:26px;\r\n  height:26px;\r\n  border-radius:50%;\r\n  border:2px solid #d83255;\r\n  color:#d83255;\r\n  display:inline-flex;\r\n  justify-content:center;\r\n  align-items:center;\r\n  font-size:18px;\r\n  font-weight:700;\r\n  margin-right:12px;\r\n  opacity:0;\r\n  transform:scale(0.4);\r\n}\r\n\r\n.mcq-cross-icon.show{\r\n  animation:mcqCrossPop 0.35s ease forwards;\r\n}\r\n\r\n@keyframes mcqCrossPop{\r\n  70%{opacity:1;transform:scale(1.18);}\r\n  100%{opacity:1;transform:scale(1);}\r\n}\r\n\r\n.mcq-specific-feedback-text{\r\n  display:inline-block;\r\n  background:#fff4b8;\r\n  color:#111827;\r\n  padding:8px 16px;\r\n  font-size:22px;\r\n  line-height:1.35;\r\n  min-width:850px;\r\n  min-height:44px;\r\n}\r\n\r\n.mcq-submit-button{\r\n  position:absolute;\r\n  right:34px;\r\n  bottom:30px;\r\n  border:0;\r\n  border-radius:999px;\r\n  background:#1C244B;\r\n  color:#ffffff;\r\n  padding:14px 28px;\r\n  font-size:18px;\r\n  font-weight:600;\r\n  box-shadow:0 14px 32px rgba(28,36,75,0.25);\r\n  cursor:default;\r\n  transition:transform 0.2s ease,box-shadow 0.2s ease,background 0.2s ease;\r\n}\r\n\r\n.mcq-submit-button.clicked{\r\n  transform:translateY(2px) scale(0.97);\r\n  background:#26315f;\r\n  box-shadow:0 7px 18px rgba(28,36,75,0.22);\r\n}\r\n\r\n.mcq-general-feedback{\r\n  height:520px;\r\n  background:#fff3c9;\r\n  color:#8a6a00;\r\n  padding:26px 30px 28px;\r\n  font-size:23px;\r\n  line-height:1.34;\r\n  opacity:0;\r\n  transform:translateY(20px);\r\n  transition:opacity 0.7s ease,transform 0.7s ease;\r\n  overflow:hidden;\r\n}\r\n\r\n.mcq-general-feedback.show{\r\n  opacity:1;\r\n  transform:translateY(0);\r\n}\r\n\r\n#mcqGeneralText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.mcq-specific-cursor{background:#111827;}\r\n.mcq-general-cursor{background:#8a6a00;}\r\n\r\n.ols-saq-screen{\r\n  width:1360px;\r\n  height:965px;\r\n  border-radius:22px;\r\n  overflow:hidden;\r\n  background:#eaf0ff;\r\n  box-shadow:0 26px 70px rgba(28,36,75,0.22);\r\n  opacity:0;\r\n  transform:translateY(24px) scale(0.96);\r\n}\r\n\r\n.ols-saq-screen.show{\r\n  animation:olsSaqScreenEnter 1s ease forwards;\r\n}\r\n\r\n@keyframes olsSaqScreenEnter{\r\n  from{opacity:0;transform:translateY(24px) scale(0.96);}\r\n  to{opacity:1;transform:translateY(0) scale(1);}\r\n}\r\n\r\n.saq-question-area{\r\n  height:335px;\r\n  background:#eaf0ff;\r\n  padding:30px 40px 32px;\r\n}\r\n\r\n.saq-question-text{\r\n  font-size:25px;\r\n  line-height:1.42;\r\n  color:#111827;\r\n  margin-bottom:22px;\r\n}\r\n\r\n.saq-student-box{\r\n  height:195px;\r\n  background:#f3f4f6;\r\n  border:2px solid #cfd6e3;\r\n  border-radius:8px;\r\n  padding:23px 26px;\r\n  font-size:24px;\r\n  line-height:1.55;\r\n  color:#4b5563;\r\n  position:relative;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback{\r\n  height:630px;\r\n  background:#dff3e6;\r\n  color:#075f3b;\r\n  padding:28px 40px 30px;\r\n  font-size:23px;\r\n  line-height:1.47;\r\n  opacity:0;\r\n  transform:translateY(20px);\r\n  transition:opacity 0.7s ease,transform 0.7s ease;\r\n  overflow:hidden;\r\n}\r\n\r\n.saq-teacher-feedback.show{\r\n  opacity:1;\r\n  transform:translateY(0);\r\n}\r\n\r\n#saqTeacherText{\r\n  white-space:pre-wrap;\r\n}\r\n\r\n.saq-teacher-cursor{\r\n  background:#075f3b;\r\n}\r\n\r\n@media(max-width:900px){\r\n  .ols-video-title,\r\n  .ols-mcq-intro-title,\r\n  .ols-saq-intro-title{\r\n    font-size:clamp(42px,11vw,78px);\r\n    line-height:1.12;\r\n  }\r\n\r\n  .ols-title-cursor{\r\n    width:4px;\r\n    margin-left:6px;\r\n  }\r\n\r\n  .ols-video-card{\r\n    border-radius:20px;\r\n  }\r\n}\r\n<\/style>\r\n<\/head>\r\n\r\n<body>\r\n<div class=\"ols-combined-stage\">\r\n\r\n  <section id=\"sceneVideo\" class=\"ols-scene active\">\r\n    <div class=\"ols-video-stage\">\r\n      <div id=\"videoTitleScreen\" class=\"ols-video-title-screen\">\r\n        <div class=\"ols-video-title-wrap\">\r\n          <h1 class=\"ols-video-title\">\r\n            <span id=\"videoTitleText\"><\/span><span id=\"videoTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <section id=\"videoScene\" class=\"ols-video-scene\">\r\n        <div class=\"ols-video-scale-wrap\">\r\n          <div class=\"ols-video-card\">\r\n            <video\r\n              id=\"lessonVideo\"\r\n              src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Virtual-Lesson.mp4\"\r\n              muted\r\n              playsinline\r\n              preload=\"auto\">\r\n            <\/video>\r\n          <\/div>\r\n        <\/div>\r\n      <\/section>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneMcq\" class=\"ols-scene\">\r\n    <div class=\"ols-mcq-stage\">\r\n      <div id=\"mcqIntroScreen\" class=\"ols-mcq-intro-screen\">\r\n        <div class=\"ols-mcq-intro-title-wrap\">\r\n          <h1 class=\"ols-mcq-intro-title\">\r\n            <span id=\"mcqIntroTitleText\"><\/span><span id=\"mcqIntroTitleCursor\" class=\"ols-title-cursor\"><\/span>\r\n          <\/h1>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"ols-mcq-scale-wrap\">\r\n        <main id=\"mcqScreen\" class=\"ols-mcq-screen\">\r\n          <section class=\"mcq-question-area\">\r\n            <p class=\"mcq-question-lead\">Some ionic radii are shown.<\/p>\r\n\r\n            <table class=\"mcq-ionic-table\">\r\n              <thead>\r\n                <tr>\r\n                  <th>Ion<\/th>\r\n                  <th>Ionic radius \/ nm<\/th>\r\n                <\/tr>\r\n              <\/thead>\r\n              <tbody>\r\n                <tr><td>Na<sup>+<\/sup><\/td><td>0.102<\/td><\/tr>\r\n                <tr><td>K<sup>+<\/sup><\/td><td>0.138<\/td><\/tr>\r\n                <tr><td>F<sup>\u2212<\/sup><\/td><td>0.133<\/td><\/tr>\r\n                <tr><td>Cl<sup>\u2212<\/sup><\/td><td>0.180<\/td><\/tr>\r\n              <\/tbody>\r\n            <\/table>\r\n\r\n            <p class=\"mcq-question-main\">Which compound has the strongest ionic bonding?<\/p>\r\n\r\n            <div class=\"mcq-options-wrap\">\r\n              <div id=\"mcqWrongOption\" class=\"mcq-option-row\">\r\n                <span class=\"mcq-radio\"><\/span>\r\n                <span class=\"mcq-radio-ripple\"><\/span>\r\n                <span class=\"mcq-option-label\">sodium chloride<\/span>\r\n\r\n                <span id=\"mcqSpecificFeedback\" class=\"mcq-specific-feedback\">\r\n                  <span id=\"mcqCrossIcon\" class=\"mcq-cross-icon\">\u00d7<\/span>\r\n                  <span class=\"mcq-specific-feedback-text\">\r\n                    <span id=\"mcqSpecificText\"><\/span><span id=\"mcqSpecificCursor\" class=\"cursor mcq-specific-cursor\" style=\"display:none;\"><\/span>\r\n                  <\/span>\r\n                <\/span>\r\n              <\/div>\r\n\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium chloride<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">sodium fluoride<\/span><\/div>\r\n              <div class=\"mcq-option-row\"><span class=\"mcq-radio\"><\/span><span class=\"mcq-radio-ripple\"><\/span><span class=\"mcq-option-label\">potassium fluoride<\/span><\/div>\r\n            <\/div>\r\n\r\n            <button id=\"mcqSubmitButton\" class=\"mcq-submit-button\">Submit answer<\/button>\r\n          <\/section>\r\n\r\n          <section id=\"mcqGeneralFeedback\" class=\"mcq-general-feedback\">\r\n            <span id=\"mcqGeneralText\"><\/span><span id=\"mcqGeneralCursor\" class=\"cursor mcq-general-cursor\" style=\"display:none;\"><\/span>\r\n          <\/section>\r\n        <\/main>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section id=\"sceneSaq\" class=\"ols-scene\">\r\n    <div class=\"ols-saq-stage\">\r\n      <div id=\"saqIntro\" class=\"ols-saq-intro\">\r\n        <div 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the ions can get closer together.\\n\"+\r\n\"\u2022 Smaller ions \u2192 stronger electrostatic attraction \u2192 stronger ionic lattice.\\n\"+\r\n\"\u2022 Na\u207a (0.102 nm) is smaller than K\u207a (0.138 nm).\\n\"+\r\n\"\u2022 F\u207b (0.133 nm) is smaller than Cl\u207b (0.180 nm).\\n\\n\"+\r\n\"Therefore, the strongest ionic bonding occurs in the compound formed by the smallest cation and the smallest anion \u2192 sodium fluoride (NaF).\\n\\n\"+\r\n\"The correct answer is: sodium fluoride\";\r\n\r\nconst mcqIntroScreen=document.getElementById(\"mcqIntroScreen\");\r\nconst mcqIntroTitleText=document.getElementById(\"mcqIntroTitleText\");\r\nconst mcqIntroTitleCursor=document.getElementById(\"mcqIntroTitleCursor\");\r\nconst mcqScreen=document.getElementById(\"mcqScreen\");\r\nconst mcqWrongOption=document.getElementById(\"mcqWrongOption\");\r\nconst mcqSubmitButton=document.getElementById(\"mcqSubmitButton\");\r\nconst 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because it has more atoms packed together and melts at a higher temperature than sodium.\";\r\nconst saqTeacherFeedbackText=\r\n\"Comment:\\n\"+\r\n\"This answer is not correct. Melting temperature is a result of bonding strength, not the cause of it.\\n\\n\"+\r\n\"In metallic bonding, positive metal ions are attracted to a sea of delocalised electrons. The strength of this attraction depends on the charge of the ions and the number of delocalised electrons.\\n\\n\"+\r\n\"Magnesium forms Mg\u00b2\u207a ions and contributes two delocalised electrons per atom, whereas sodium forms Na\u207a ions and contributes only one electron. This results in a stronger electrostatic attraction in magnesium. Additionally, Mg\u00b2\u207a ions have a higher charge density than Na\u207a ions, further strengthening the metallic bonding.\\n\\n\"+\r\n\"Next time, include:\\n\"+\r\n\"\u2022 Ion charge: magnesium forms Mg\u00b2\u207a, sodium forms Na\u207a \u2713\\n\"+\r\n\"\u2022 Delocalised electrons: magnesium provides more electrons to the sea \u2713\\n\"+\r\n\"\u2022 Charge density: smaller, more highly charged ions create stronger attraction \u2713\\n\\n\"+\r\n\"You were close. 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The sulfur reacts with oxygen to form SO<sub>2<\/sub>.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>What is the equation for sulfur burning in oxygen?<\/h3>\n            <p>The balanced equation is S + O<sub>2<\/sub> \u2192 SO<sub>2<\/sub>.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>How does sulfur dioxide cause acid rain?<\/h3>\n            <p>Sulfur dioxide is an acidic gas. Once released into the atmosphere, it dissolves in rainwater and contributes to the formation of acid rain.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>Why is coal an important source of sulfur dioxide pollution?<\/h3>\n            <p>Coal often contains a relatively high sulfur content, so burning coal in power stations can release large quantities of sulfur oxides.<\/p>\n          <\/div>\n\n          <div class=\"ols-faq-item\">\n            <h3>What damage can acid rain cause?<\/h3>\n            <p>Acid rain can damage buildings, harm aquatic life and affect soil chemistry.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Continue through the connected AQA 3.3.2 alkane combustion and pollution pages.<\/p>\n        <div class=\"ols-related-grid\">\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/combustion\/\">Combustion<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/reactions\/free-radical-substitution\/\">Reactions of Alkanes<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-4-alkenes\/alkene-bonding\/\">Alkenes<\/a>\n        <\/div>\n      <\/section>\n\n      \n\n      <!-- OLS Author Copyright Footprint \/ Attribution Card -->\n      <section class=\"ols-attribution-card\">\n        <style>\n          .ols-attribution-card {\n            background: linear-gradient(135deg, #ffffff, #f8fbff);\n            border: 1px solid rgba(28, 36, 75, 0.14);\n            border-radius: 28px;\n            box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n            padding: 34px;\n            margin-bottom: 24px;\n            overflow: hidden;\n            font-family: Poppins, Arial, sans-serif;\n            box-sizing: border-box;\n          }\n      \n          .ols-attribution-card,\n          .ols-attribution-card * {\n            box-sizing: border-box;\n          }\n      \n          .ols-attribution-card p {\n            margin: 0;\n            font-size: 14px;\n            line-height: 1.65;\n            font-weight: 300;\n            color: #667085;\n          }\n      \n          .ols-attribution-card strong {\n            font-weight: 700;\n            color: #1C244B;\n          }\n      \n          @media (max-width: 760px) {\n            .ols-attribution-card {\n              padding: 24px 18px;\n              border-radius: 22px;\n            }\n          }\n        <\/style>\n      \n        <p><strong>Copyright notice:<\/strong> This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.<\/p>\n      <\/section>\n      <script type=\"application\/ld+json\">{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"WebPage\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/\",\n      \"name\": \"Flue-Gas Desulfurisation - AQA A Level Chemistry\",\n      \"description\": \"AQA A Level Chemistry 3.3.2.3 revision notes on flue-gas desulfurisation: removing sulfur dioxide with calcium oxide or calcium carbonate, the neutralisation equations, gypsum formation and the advantages of each method.\",\n      \"inLanguage\": \"en-GB\",\n      \"isPartOf\": {\n        \"@type\": \"WebSite\",\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/#website\",\n        \"name\": \"Online Learning System\",\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n      },\n      \"about\": [\n        {\n          \"@type\": \"Thing\",\n          \"name\": \"Sulfur dioxide\"\n        },\n        {\n          \"@type\": \"Thing\",\n          \"name\": \"Acid rain\"\n        },\n        {\n          \"@type\": \"Thing\",\n          \"name\": \"Combustion pollution\"\n        },\n        {\n          \"@type\": \"Thing\",\n          \"name\": \"Alkanes as fuels\"\n        }\n      ],\n      \"author\": {\n        \"@type\": \"Person\",\n        \"name\": \"Dr. Mohammed Al-Fatah\"\n      },\n      \"publisher\": {\n        \"@type\": \"Organization\",\n        \"name\": \"Online Learning System\",\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/\"\n      },\n      \"breadcrumb\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/#breadcrumb\"\n      },\n      \"mainEntity\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/#faq\"\n      }\n    },\n    {\n      \"@type\": \"BreadcrumbList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/flue-gas-desulfurisation\/#breadcrumb\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"name\": \"Revision Notes\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"name\": \"A Level Chemistry\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"name\": \"AQA\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"name\": \"3.3.2 Alkanes\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 5,\n          \"name\": \"Alkanes as Fuel\",\n          \"item\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/aqa\/3-3-2-alkanes\/fuel\/\"\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 6,\n          \"name\": \"Flue-Gas Desulfurisation - 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