{"id":3539,"date":"2026-05-14T08:11:04","date_gmt":"2026-05-14T07:11:04","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/?page_id=3539"},"modified":"2026-06-28T05:54:02","modified_gmt":"2026-06-28T04:54:02","slug":"oxides-of-sulfur","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-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, 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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    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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    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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 4 Organic Chemistry &amp; Alkanes<\/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-international\/topic-4-organic-chemistry-and-alkanes\/hazard-and-risk\/\">Hazard &amp; Risk<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/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-international\/topic-4-organic-chemistry-and-alkanes\/organic-chemistry\/ester\/\">Ester<\/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-international\/topic-4-organic-chemistry-and-alkanes\/isomerism\/\">Isomerism<\/a>\r\n      <\/li>\r\n\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-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-international\/topic-4-organic-chemistry-and-alkanes\/reactions\/further-substitution\/\">Further Substitution<\/a>\r\n          <\/li>\r\n        <\/ul>\r\n      <\/li>\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-international\/topic-5-alkenes\/\">Alkenes<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-6-energetics\/\">Energetics<\/a>\r\n      <\/li>\r\n      <li>\r\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-7-intermolecular-forces\/\">Intermolecular Forces<\/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 = 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href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Edexcel International<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/\">Topic 4 Organic Chemistry &amp; 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\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel International<\/div>\n          <div class=\"ols-badge\">Topic 4: Organic Chemistry &amp; Alkanes<\/div>\n          <div class=\"ols-badge\">Alkanes as Fuel: Oxides of Sulfur<\/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      <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\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>Sulfur present as an element reacts directly with oxygen during combustion. The balanced equation is:<\/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>Sulfur can also be present inside organic molecules. 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\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>Acid rain is a major environmental problem because it can damage buildings, harm aquatic life and affect soil chemistry.<\/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\/05\/oxides-of-sulfur.webp\" alt=\"Sulfur dioxide pollution from combustion contributing to acid rain\" 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\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><strong>Coal often contains a relatively high 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\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      <\/article>\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\n      <section class=\"ols-h5p-card\">\n        <h2>Check Your Understanding<\/h2>\n        <p>Use these short activities to check the key ideas before moving on to oxides of nitrogen and catalytic converters.<\/p>\n\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=\"T4.5.2.1 Drag: Oxides of Sulfur Key Concepts\"><\/iframe><\/div><\/div>\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=\"T4.5.2.2 MCQ: Formation of Sulfur Dioxide\"><\/iframe><\/div><\/div>\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=\"T4.5.2.3 MCQ: Sulfur Dioxide and Acid Rain\"><\/iframe><\/div><\/div>\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=\"T4.5.2.4 MCQ: Coal and Environmental Effects\"><\/iframe><\/div><\/div>\n      <\/section>\n\n      <section class=\"ols-course-cta-topic4\" id=\"olsCourseCtaTopic4001\">\n        <div class=\"ols-course-cta-card\">\n          <div class=\"ols-course-cta-top\">\n            <a class=\"ols-course-cta-image-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\" aria-label=\"Open the Edexcel International A Level Chemistry Topic 4 Organic Chemistry and Alkanes course page\">\n              <div class=\"ols-course-cta-image\">\n                <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-4a-4b-organic-chemistry-alkanes-course-banner.jpg\" alt=\"Edexcel International A Level Chemistry Topic 4 Organic Chemistry and Alkanes course banner\">\n              <\/div>\n            <\/a>\n\n            <div class=\"ols-course-cta-content\">\n              <div class=\"ols-course-cta-header-row\">\n                <div class=\"ols-course-cta-kicker\">Complete Topic 4 Organic Chemistry &amp; Alkanes Course<\/div>\n                <a class=\"ols-course-button ols-course-button-top\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\">View Course<\/a>\n              <\/div>\n\n              <h2>Master Organic Chemistry &amp; Alkanes for Edexcel International A Level Chemistry<\/h2>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-course-cta-intro-stats\">\n            <p class=\"ols-course-cta-intro\">\n              Continue from these free revision notes into the full Topic 4 Organic Chemistry &amp; Alkanes course, with guided video teaching, diagnostic MCQ practice, teacher-marked short-answer questions and a specification assignment with a personalised progress report.\n            <\/p>\n\n            <div class=\"ols-course-cta-stats\">\n              <div class=\"ols-course-stat\">\n                <span>Course type<\/span>\n                <strong>Guided revision<\/strong>\n              <\/div>\n              <div class=\"ols-course-stat\">\n                <span>Exam board<\/span>\n                <strong>Edexcel IAL<\/strong>\n              <\/div>\n              <div class=\"ols-course-stat\">\n                <span>Practice<\/span>\n                <strong>MCQs + SAQs<\/strong>\n              <\/div>\n              <div class=\"ols-course-stat\">\n                <span>Feedback<\/span>\n                <strong>Progress report<\/strong>\n              <\/div>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-course-cta-features\">\n            <div class=\"ols-course-feature\">\n              <h3>Guided video teaching<\/h3>\n              <p>Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.<\/p>\n            <\/div>\n            <div class=\"ols-course-feature\">\n              <h3>Instant MCQ feedback<\/h3>\n              <p>Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.<\/p>\n            <\/div>\n            <div class=\"ols-course-feature\">\n              <h3>Teacher-marked SAQs<\/h3>\n              <p>Submit written exam responses and receive chemistry specialist feedback with improvement guidance.<\/p>\n            <\/div>\n            <div class=\"ols-course-feature\">\n              <h3>Progress tracking<\/h3>\n              <p>Identify strengths and weaknesses across the full Topic 4 specification with targeted reporting.<\/p>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-course-cta-bottom\">\n            <a class=\"ols-course-button\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/organic-chemistry-alkanes-topic-4ab-edexcel-international\/\">View Organic Chemistry &amp; Alkanes Topic 4 Course<\/a>\n          <\/div>\n        <\/div>\n      <\/section>\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      <section class=\"ols-related-card\">\n        <h2>Related Topics<\/h2>\n        <p>Continue through the connected Topic 4 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-international\/\">Combustion<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Oxides of Nitrogen<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Catalytic Converter<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-4-organic-chemistry-and-alkanes\/alternative-fuel\/\">Alternative Fuel<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\">Reactions of Alkanes<\/a>\n          <a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/topic-5-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\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-international\/#webpage\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel-international\/\",\n            \"name\": \"Oxides of Sulfur | Edexcel International A Level Chemistry Revision Notes\",\n            \"description\": \"Revision notes on oxides of sulfur for Edexcel International A Level Chemistry, including sulfur dioxide formation, sulfur impurities in fuels, coal combustion, acid rain and environmental effects.\",\n            \"inLanguage\": \"en-GB\",\n            \"isPartOf\": {\n              \"@type\": 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