{"id":4828,"date":"2026-06-03T06:24:32","date_gmt":"2026-06-03T05:24:32","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/"},"modified":"2026-10-14T09:06:57","modified_gmt":"2026-10-14T08:06:57","slug":"oxides-of-sulfur","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/","title":{"rendered":"Oxides of Sulfur"},"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    <\/style>\n\n  <aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Topic 6 Organic Chemistry I<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/\">Introduction to Organic Chemistry<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/iupac-rules\/\">IUPAC Rules<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alkene\/\">Alkene<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/alcohol\/\">Alcohol<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/aldehyde\/\">Aldehyde<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ketone\/\">Ketone<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/carboxylic-acid\/\">Carboxylic Acid<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/ester\/\">Ester<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/introduction-to-organic-chemistry\/isomerism\/\">Isomerism<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/\">Alkanes from Crude Oil<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/fractional-distillation\/\">Fractional Distillation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/cracking\/\">Cracking<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/crude-oil\/reforming\/\">Reforming<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/\">Alkanes as Fuel<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/combustion\/\">Combustion<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/\">Oxides of Sulfur<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-nitrogen\/\">Oxides of Nitrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/\">Reactions of Alkanes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/free-radical-substitution\/\">Free Radical Substitution<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/initiation\/\">Initiation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/propagation\/\">Propagation<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/termination\/\">Termination<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/\">Alkenes<\/a>\r\n\r\n        <ul class=\"ols-subtopic-list\">\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/alkene-bonding\/\">Alkene Bonding<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/geometric-isomerism\/\">Geometric Isomerism<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/electrophilic-addition-mechanism\/\">Electrophilic Addition Mechanism<\/a>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/\">Reactions of Alkenes<\/a>\r\n\r\n            <ul class=\"ols-subtopic-list\">\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/halogens\/\">Halogens<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen-halide\/\">Hydrogen Halide<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/bromine-water\/\">Bromine Water<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/hydrogen\/\">Hydrogen<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/steam\/\">Steam<\/a>\r\n              <\/li>\r\n              <li>\r\n                <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/reactions-of-alkenes\/kmno4\/\">KMnO4<\/a>\r\n              <\/li>\r\n            <\/ul>\r\n          <\/li>\r\n\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymerisation-reactions\/\">Polymerisation Reactions<\/a>\r\n          <\/li>\r\n          <li>\r\n            <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkenes\/polymer-waste\/\">Polymer Waste<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/halogenoalkanes\/\">Halogenoalkanes<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alcohols\/\">Alcohols<\/a>\r\n      <\/li>\r\n\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Next Topics<\/h4>\r\n\r\n    <ul class=\"ols-topic-list\">\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-7-modern-analytical-techniques-i\/\">Topic 7 Modern Analytical Techniques I<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Topic 5 Formulae, Equations &amp; Amounts<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-4-inorganic-chemistry-and-the-periodic-table\/\">Topic 4 Inorganic Chemistry &amp; The Periodic Table<\/a>\r\n      <\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function() {\r\n  function normalisePath(path) {\r\n    return String(path || '')\r\n      .split('?')[0]\r\n      .split('#')[0]\r\n      .replace(\/\\\/+$\/, '')\r\n      .toLowerCase();\r\n  }\r\n\r\n  function highlightActive() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      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parentSub = matched.closest('.ols-subtopic-list');\r\n\r\n      if (parentSub) {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('active');\r\n          matched.setAttribute('aria-current', 'page');\r\n        }\r\n\r\n        var parentLi = parentSub.closest('li');\r\n        while (parentLi) {\r\n          parentLi.classList.add('parent-active', 'active-main');\r\n\r\n          var parentLink = parentLi.querySelector(':scope > a');\r\n          if (parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n\r\n          var higherSub = parentLi.parentElement.closest('.ols-subtopic-list');\r\n          parentLi = higherSub ? higherSub.closest('li') : null;\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', 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\/edexcel\/\">Edexcel<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/\">Topic 6 Organic Chemistry I<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/\">Alkanes<\/a> \/\n        <span>Oxides of Sulfur<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Oxides of Sulfur<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to sulfur dioxide pollution from combustion, sulfur-containing impurities in fuels, coal as a sulfur dioxide source, acid rain and environmental effects.<\/p>\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Paper 2<\/div>\n          <div class=\"ols-badge\">Topic 6: Organic Chemistry I<\/div>\n          <div class=\"ols-badge\">9CH0\/02<\/div>\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: Acidic Oxides, pH and Carbonates<\/h2>\n<p>Before you start, check the GCSE ideas about acids that explain how acid rain forms and what it does.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"687\"><\/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>Where Sulfur Dioxide Comes From<\/h2>\n        <\/div>\n\n        <p>Some <strong>petroleum fractions contain sulfur-based impurities<\/strong>. When these fuels are burned, the sulfur impurities are oxidised and form <strong>sulfur dioxide, SO<sub>2<\/sub><\/strong>.<\/p>\n        <p>This means combustion can release pollutants even when the hydrocarbon fuel itself mainly contains carbon and hydrogen. The pollution comes from <strong>impurities mixed with the fuel<\/strong> or from sulfur-containing organic molecules present in the fuel source.<\/p>\n\n        <div class=\"ols-reaction-summary\">\n          <div class=\"ols-summary-item\"><span>Main pollutant<\/span><strong>Sulfur dioxide, SO<sub>2<\/sub><\/strong><\/div>\n          <div class=\"ols-summary-item\"><span>Source in fuels<\/span><strong>Sulfur-based impurities<\/strong><\/div>\n          <div class=\"ols-summary-item\"><span>Combustion link<\/span><strong>Sulfur reacts with oxygen<\/strong><\/div>\n          <div class=\"ols-summary-item\"><span>Environmental concern<\/span><strong>Acid rain formation<\/strong><\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> Sulfur dioxide is not produced from pure alkanes alone. It forms when sulfur-containing substances in the fuel are burned.<\/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: Which Fuels Give SO\u2082?<\/h2>\n<p>Click every substance that would give sulfur dioxide when it burns.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-116\" class=\"h5p-iframe\" data-content-id=\"116\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Oxides of Sulfur Mark the Words: Which Substances Give SO\u2082 When Burned?\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Formation of Sulfur Dioxide<\/h2>\n        <\/div>\n\n        <p>In fuels the sulfur is nearly always <strong>combined in compounds<\/strong> rather than present as the element. Whatever it is combined with, the sulfur is oxidised to sulfur dioxide when the fuel burns, so examiners accept this simplified equation:<\/p>\n\n        <div class=\"ols-definition-box\">\n          <p><strong>S + O<sub>2<\/sub> \u2192 SO<sub>2<\/sub><\/strong><\/p>\n        <\/div>\n\n        <p>Most often the sulfur sits inside an organic molecule. For example, <strong>methanethiol, CH<sub>3<\/sub>SH<\/strong>, burns to form sulfur dioxide alongside carbon dioxide and water.<\/p>\n\n        <div class=\"ols-definition-box\">\n          <p><strong>CH<sub>3<\/sub>SH + 3O<sub>2<\/sub> \u2192 SO<sub>2<\/sub> + CO<sub>2<\/sub> + 2H<sub>2<\/sub>O<\/strong><\/p>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> When sulfur is present in the fuel, combustion produces sulfur dioxide. Do not confuse this with incomplete combustion, which produces carbon monoxide or soot.<\/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: Balance the Equations<\/h2>\n<p>Type the missing balancing numbers for three sulfur compounds the page does not show.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-117\" class=\"h5p-iframe\" data-content-id=\"117\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Oxides of Sulfur Fill the Blanks: Balancing Equations for Burning Sulfur Compounds\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>Sulfur Dioxide and Acid Rain<\/h2>\n        <\/div>\n\n        <p><strong>Sulfur dioxide is an acidic gas.<\/strong> Once released into the atmosphere, it can dissolve in rainwater and contribute to the formation of <strong>acid rain<\/strong>.<\/p>\n        <p>Sulfur dioxide dissolves in rainwater to give <strong>sulfurous acid<\/strong>, H<sub>2<\/sub>SO<sub>3<\/sub>:<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>SO<sub>2<\/sub> + H<sub>2<\/sub>O \u2192 H<sub>2<\/sub>SO<sub>3<\/sub><\/strong><\/p>\n        <\/div>\n        <p>In the atmosphere some sulfur dioxide is oxidised to <strong>sulfur trioxide, SO<sub>3<\/sub><\/strong>, the other oxide of sulfur, which dissolves to give the stronger <strong>sulfuric acid<\/strong>, H<sub>2<\/sub>SO<sub>4<\/sub>:<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>2SO<sub>2<\/sub> + O<sub>2<\/sub> \u2192 2SO<sub>3<\/sub><\/strong><\/p>\n          <p><strong>SO<sub>3<\/sub> + H<sub>2<\/sub>O \u2192 H<sub>2<\/sub>SO<sub>4<\/sub><\/strong><\/p>\n        <\/div>\n        <p>Acid rain is a major environmental problem because it can damage buildings, harm aquatic life and affect soil chemistry.<\/p>\n<p>Limestone and marble are <strong>calcium carbonate<\/strong>, so the acid reacts with the stone itself, giving a salt, water and carbon dioxide. The salt flakes or washes off, so carved surfaces are slowly eaten away. Acid rain also corrodes metal structures.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Stage<\/th>\n                <th>Chemistry idea<\/th>\n                <th>Consequence<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Stage\"><strong>Combustion<\/strong><\/td>\n                <td data-label=\"Chemistry idea\">Sulfur-containing substances burn in oxygen.<\/td>\n                <td data-label=\"Consequence\">Sulfur dioxide, SO<sub>2<\/sub>, is released.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Stage\"><strong>Atmosphere<\/strong><\/td>\n                <td data-label=\"Chemistry idea\">SO<sub>2<\/sub> is acidic and dissolves in rainwater.<\/td>\n                <td data-label=\"Consequence\">Acid rain can form.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Stage\"><strong>Environment<\/strong><\/td>\n                <td data-label=\"Chemistry idea\">Acidic rainwater reacts with materials and ecosystems.<\/td>\n                <td data-label=\"Consequence\">Buildings, aquatic life and soils can be damaged.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/wave-65.jpg\" alt=\"Three-stage flow: sulfur burns to SO\u2082, SO\u2082 dissolves in rain, acid rain damages stone, water life and soil\" title=\"Oxides of Sulfur and Acid Rain\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <p>Sulfur dioxide released during combustion can dissolve in rainwater, contributing to acid rain and environmental damage.<\/p>\n          <\/div>\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 Damaged Statue<\/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-118\" class=\"h5p-iframe\" data-content-id=\"118\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Oxides of Sulfur Explain: The Eroded Marble Statue\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Coal and Other Sources of Sulfur Dioxide<\/h2>\n        <\/div>\n\n        <p>Coal often contains a relatively high <strong>sulfur content<\/strong>. When coal is burned in power stations, large quantities of <strong>sulfur oxides<\/strong> can be released.<\/p>\n        <p>This is why sulfur dioxide pollution is closely associated with the combustion of sulfur-containing fossil fuels, especially where fuel sulfur content is high and pollution control is limited.<\/p>\n        <p>Emissions are cut by <strong>flue gas desulfurisation<\/strong>. The waste gases are passed through a spray of <strong>calcium oxide<\/strong>, CaO, or a slurry of <strong>calcium carbonate<\/strong>, CaCO<sub>3<\/sub>.<\/p>\n<p>Both are basic, so they neutralise the acidic sulfur dioxide and it is removed as solid calcium sulfite:<\/p>\n        <div class=\"ols-definition-box\">\n          <p><strong>CaO + SO<sub>2<\/sub> \u2192 CaSO<sub>3<\/sub><\/strong><\/p>\n        <\/div>\n        <p>Sulfur compounds are also taken out of fuels at the refinery before they are sold, which is why low-sulfur petrol and diesel give less SO<sub>2<\/sub>.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Fuel or source<\/th>\n                <th>Reason SO<sub>2<\/sub> may form<\/th>\n                <th>Pollution issue<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td data-label=\"Fuel or source\"><strong>Petroleum fractions<\/strong><\/td>\n                <td data-label=\"Reason SO\u2082 may form\">May contain sulfur-based impurities.<\/td>\n                <td data-label=\"Pollution issue\">SO<sub>2<\/sub> is released during combustion.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Fuel or source\"><strong>Sulfur-containing organic molecules<\/strong><\/td>\n                <td data-label=\"Reason SO\u2082 may form\">The sulfur atom is oxidised during burning.<\/td>\n                <td data-label=\"Pollution issue\">SO<sub>2<\/sub> forms alongside CO<sub>2<\/sub> and H<sub>2<\/sub>O.<\/td>\n              <\/tr>\n              <tr>\n                <td data-label=\"Fuel or source\"><strong>Coal<\/strong><\/td>\n                <td data-label=\"Reason SO\u2082 may form\">Often has relatively high sulfur content.<\/td>\n                <td data-label=\"Pollution issue\">Large amounts of sulfur oxides can be emitted in power stations.<\/td>\n              <\/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\/10\/t4-img-56-so2solutions.jpg\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open image fullscreen\">\n<img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-56-so2solutions.jpg\" alt=\"Removing sulfur from fuel, flue-gas desulfurisation with CaO or CaCO\u2083, and acid rain reacting with limestone\" data-fullscreen-src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/10\/t4-img-56-so2solutions.jpg\">\n<\/a>\n<\/div>\n<div class=\"ols-figure-caption\"><p>Sulfur is removed from fuels before burning, and SO\u2082 is removed from flue gases by calcium oxide or calcium carbonate.<\/p><\/div>\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: How Much SO\u2082?<\/h2>\n<p>Work out the mass of sulfur dioxide on paper, then choose your answer.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-119\" class=\"h5p-iframe\" data-content-id=\"119\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Oxides of Sulfur MCQ: Mass of SO\u2082 from a Coal-Fired Power Station\"><\/iframe><\/div><\/div>\n<\/section>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>Environmental Effects to Remember<\/h2>\n        <\/div>\n\n        <p>Sulfur dioxide pollution is important because it links combustion chemistry to large-scale environmental damage. In exam answers, the strongest responses connect the <strong>source<\/strong>, the <strong>pollutant<\/strong> and the <strong>effect<\/strong>.<\/p>\n\n        <ul>\n          <li><strong>Source:<\/strong> sulfur-containing impurities or sulfur-containing fuels are burned.<\/li>\n          <li><strong>Pollutant:<\/strong> sulfur dioxide, SO<sub>2<\/sub>, is released into the atmosphere.<\/li>\n          <li><strong>Effect:<\/strong> sulfur dioxide contributes to acid rain.<\/li>\n          <li><strong>Damage:<\/strong> acid rain damages buildings, harms aquatic life and affects soil chemistry.<\/li>\n        <\/ul>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam focus:<\/strong> A precise answer should name sulfur dioxide and link it to acid rain. Avoid vague phrases such as \u201cbad gases\u201d or \u201cgeneral pollution\u201d.<\/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: Pick the Accurate Statement<\/h2>\n<p>In each round, choose the one statement that is accurate.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-688\" class=\"h5p-iframe\" data-content-id=\"688\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Oxides of Sulfur Summary: Source, Pollutant and Effect\"><\/iframe><\/div><\/div>\n<\/section>\n\n      \n\n      <section class=\"ols-faq-card\">\n        <h2>Oxides of Sulfur FAQs<\/h2>\n        <p>Common questions about sulfur dioxide pollution from combustion.<\/p>\n\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>Why does combustion produce sulfur dioxide?<\/h3>\n            <p>Combustion produces sulfur dioxide when the fuel contains sulfur-based impurities or sulfur-containing organic molecules. 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      <!-- author card (moved to the end, 10 Oct 2026) -->\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\n                class=\"ols-linkedin-pill\"\n                href=\"https:\/\/www.linkedin.com\/in\/doctormohammedfatah\/\"\n                target=\"_blank\"\n                rel=\"noopener noreferrer\"\n              >\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\n\n      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Continue through the connected Topic 6 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\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/combustion\/\">Combustion<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/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\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/catalytic-converter\/\">Catalytic Converter<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/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\/edexcel\/topic-6-organic-chemistry-i\/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 ols-attr-std\" aria-label=\"Copyright notice\">\n<style id=\"ols-attribution-card-css\">.ols-attribution-card.ols-attr-std{background:linear-gradient(135deg,#ffffff,#f8fbff);border:1px solid rgba(28,36,75,0.14);border-radius:28px;box-shadow:0 18px 45px rgba(28,36,75,0.10);padding:34px;margin:24px 0;overflow:hidden;font-family:Poppins,Arial,sans-serif;box-sizing:border-box}.ols-attribution-card.ols-attr-std *{box-sizing:border-box}.ols-attribution-card.ols-attr-std p{margin:0;font-size:14px;line-height:1.65;font-weight:300;color:#667085}.ols-attribution-card.ols-attr-std strong{font-weight:700;color:#1C244B}@media (max-width:760px){.ols-attribution-card.ols-attr-std{padding:24px 18px;border-radius:22px}}<\/style>\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{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@graph\": [\n        {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-6-organic-chemistry-i\/alkanes\/fuel\/oxides-of-sulfur\/\",\n            \"name\": \"Oxides of Sulfur | Edexcel A Level Chemistry Revision Notes\",\n            \"description\": \"Revision notes on oxides of sulfur for Edexcel A Level Chemistry, including sulfur dioxide formation, sulfur impurities in fuels, coal combustion, acid rain and environmental effects.\",\n            \"inLanguage\": \"en-GB\",\n            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