{"id":12387,"date":"2026-09-30T19:40:48","date_gmt":"2026-09-30T18:40:48","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/heterogeneous-and-homogeneous-catalysis\/"},"modified":"2026-10-03T11:51:52","modified_gmt":"2026-10-03T10:51:52","slug":"heterogeneous-and-homogeneous-catalysis","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/heterogeneous-and-homogeneous-catalysis\/","title":{"rendered":"Heterogeneous and Homogeneous Catalysis"},"content":{"rendered":"\n<section class=\"ols-revision-page ols-nature-of-covalent-bonding-9ch0-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      --soft-orange: #fff7ed;\n      --grey-text: #667085;\n   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width: 92px; height: 92px; border-radius: 50%; object-fit: cover; object-position: center; flex-shrink: 0; border: 4px solid #ffffff; box-shadow: 0 14px 32px rgba(28,36,75,0.18), 0 0 0 1px rgba(28,36,75,0.10); transition: transform 0.25s ease, box-shadow 0.25s ease; }\n    .ols-author:hover .ols-author-avatar-img { transform: scale(1.04); box-shadow: 0 20px 42px rgba(28,36,75,0.22), 0 0 0 1px rgba(28,36,75,0.10); }\n    .ols-author-content { min-width: 0; }\n    .ols-author-title { margin: 0 0 4px; font-size: clamp(24px,3vw,34px); line-height: 1.15; font-weight: 700; color: var(--navy); letter-spacing: -0.03em; }\n    .ols-author-description { margin: 0; font-size: 17px; line-height: 1.7; font-weight: 300; color: var(--grey-text); }\n    .ols-linkedin-pill { display: inline-flex; align-items: center; justify-content: center; gap: 10px; margin-top: 16px; padding: 11px 18px; border-radius: 999px; background: linear-gradient(135deg,#0A66C2,#004182); color: #ffffff; text-decoration: none; font-size: 14px; line-height: 1; font-weight: 700; letter-spacing: 0.01em; box-shadow: 0 10px 22px rgba(10,102,194,0.24); position: relative; overflow: hidden; transition: transform 0.22s ease, box-shadow 0.22s ease; }\n    .ols-linkedin-pill::before { content: \"\"; position: absolute; top: 0; left: -120%; width: 100%; height: 100%; background: linear-gradient(120deg, rgba(255,255,255,0) 0%, rgba(255,255,255,0.28) 50%, rgba(255,255,255,0) 100%); transition: left 0.7s ease; }\n    .ols-linkedin-pill:hover { transform: translateY(-3px) scale(1.03); box-shadow: 0 16px 34px rgba(10,102,194,0.34), 0 0 0 6px rgba(10,102,194,0.10); color: #ffffff; }\n    .ols-linkedin-pill:hover::before { left: 120%; }\n    .ols-linkedin-icon { width: 18px; height: 18px; display: block; flex-shrink: 0; }\n\n    .ols-note-card.soft { background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%); }\n    .ols-note-card.purple { background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%); }\n    .ols-note-card.orange { background: linear-gradient(135deg, #ffffff 0%, var(--soft-orange) 100%); }\n    .ols-note-title { display: flex; align-items: center; gap: 14px; margin-bottom: 20px; }\n    .ols-note-icon { width: 52px; height: 52px; border-radius: 16px; background: var(--navy); color: #ffffff; display: grid; place-items: center; font-size: 24px; font-weight: 800; flex-shrink: 0; }\n    .ols-note-title h2, .ols-h5p-card h2, .ols-related-card h2, .ols-faq-card h2 { margin: 0; font-size: clamp(28px, 3.5vw, 42px); line-height: 1.15; font-weight: 800; color: #111827; letter-spacing: -0.03em; }\n    .ols-h5p-card h2, .ols-related-card h2, .ols-faq-card h2 { margin-bottom: 14px; }\n    .ols-note-card p, .ols-note-card li { font-size: clamp(15px, 1.25vw, 17px); line-height: 1.65; font-weight: 300; color: var(--body-text); }\n    .ols-h5p-card p, .ols-related-card p, .ols-faq-card p { font-size: clamp(15px, 1.3vw, 18px); line-height: 1.65; font-weight: 300; color: var(--body-text); }\n    .ols-note-card strong, .ols-h5p-card strong, .ols-related-card strong, .ols-faq-card strong { font-weight: 700; color: var(--navy); }\n    .ols-note-card ul, .ols-note-card ol { margin: 0; padding-left: 22px; }\n\n    .ols-key-box { margin-top: 20px; background: var(--soft-green); border: 1px solid rgba(63, 143, 70, 0.25); border-radius: 20px; padding: 18px 20px; }\n    .ols-key-box p { margin: 0; font-weight: 400; color: var(--navy); }\n    .ols-definition-box { background: linear-gradient(135deg, #ffffff, var(--soft-purple)); border: 2px dashed rgba(122, 62, 157, 0.35); border-radius: 24px; padding: 22px 24px; margin-top: 22px; }\n    .ols-definition-box p { margin: 0; color: var(--navy); font-weight: 400; }\n\n    .ols-rule-list { display: grid; gap: 14px; margin-top: 18px; }\n    .ols-rule-item { background: #ffffff; border: 1px solid var(--border); border-left: 5px solid var(--blue); border-radius: 18px; padding: 18px; box-shadow: var(--inner-shadow); }\n    .ols-rule-item h3 { margin: 0 0 8px; font-size: 20px; line-height: 1.25; color: var(--navy); }\n    .ols-rule-item p { margin: 0; font-size: 15px; line-height: 1.6; }\n\n    .ols-figure-card { margin: 26px auto 4px; border: 1px solid var(--border); border-radius: 26px; overflow: hidden; background: #ffffff; box-shadow: var(--inner-shadow); max-width: 100%; }\n    .ols-figure-card.medium { max-width: 820px; }\n    .ols-figure-card.compact { max-width: 700px; }\n    .ols-figure-image { width: 100%; min-height: 260px; display: flex; align-items: center; justify-content: center; background: #ffffff; padding: 20px; }\n    .ols-figure-image img { max-width: 100%; height: auto; display: block; }\n    .ols-figure-caption { padding: 18px 24px 22px; background: linear-gradient(135deg, #ffffff, #f8fbff); border-top: 1px solid var(--border); }\n    .ols-figure-caption p { margin: 0; color: #5f6b85; font-size: clamp(15px, 1.3vw, 17px); line-height: 1.6; font-weight: 300; font-style: italic; }\n    .ols-zoom-card, .ols-zoom-card * { box-sizing: border-box; }\n    .ols-zoom-card { display: block !important; margin: 26px auto 34px !important; border: 1px solid rgba(28, 36, 75, 0.14) !important; border-radius: 26px !important; background: #ffffff !important; box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10) !important; overflow: visible !important; position: relative !important; z-index: 1 !important; isolation: isolate !important; }\n    .ols-zoom-card.medium { max-width: 820px; }\n    .ols-zoom-card.compact { max-width: 700px; }\n    .ols-zoom-card.wide { max-width: 940px; }\n    .ols-zoom-card.slim { max-width: 600px; }\n    .ols-zoom-card:hover { z-index: 50 !important; }\n    .ols-zoom-card-image { display: flex !important; align-items: center !important; justify-content: center !important; width: 100% !important; min-height: 240px !important; padding: 20px !important; background: #ffffff !important; overflow: visible !important; border-top-left-radius: 26px !important; border-top-right-radius: 26px !important; position: relative !important; z-index: 2 !important; }\n    .ols-zoom-card img.ols-zoomable-img { display: block !important; max-width: 100% !important; height: auto !important; border-radius: 18px !important; cursor: zoom-in !important; pointer-events: auto !important; user-select: none !important; -webkit-user-drag: none !important; transform: translateZ(0) scale(1) !important; transform-origin: center center !important; transition: transform 0.32s ease, box-shadow 0.32s ease, filter 0.32s ease !important; position: relative !important; z-index: 2 !important; }\n    @media (hover: hover) and (pointer: fine) { .ols-zoom-card img.ols-zoomable-img:hover { transform: translateZ(0) scale(1.35) !important; box-shadow: 0 28px 70px rgba(28, 36, 75, 0.34) !important; filter: saturate(1.02) contrast(1.01) !important; z-index: 100 !important; } }\n    .ols-zoom-card-caption { padding: 18px 22px 20px !important; background: linear-gradient(135deg, #ffffff, #f8fbff) !important; border-bottom-left-radius: 26px !important; border-bottom-right-radius: 26px !important; position: relative !important; z-index: 1 !important; }\n    .ols-zoom-card-caption p { margin: 0 !important; color: #5f6b85 !important; font-size: 15px !important; line-height: 1.65 !important; font-weight: 300 !important; font-style: italic !important; font-family: Poppins, Arial, sans-serif !important; }\n    .ols-image-lightbox { position: fixed; inset: 0; z-index: 999999; display: none; align-items: center; justify-content: center; padding: 34px; background: rgba(10, 15, 35, 0.86); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px); }\n    .ols-image-lightbox.is-open { display: flex; }\n    .ols-image-lightbox-inner { position: relative; width: min(96vw, 1500px); max-height: 92vh; display: flex; align-items: center; justify-content: center; }\n    .ols-image-lightbox-img { display: block; max-width: 100%; max-height: 92vh; height: auto; width: auto; border-radius: 22px; background: #ffffff; box-shadow: 0 32px 90px rgba(0, 0, 0, 0.45); object-fit: contain; }\n    .ols-image-lightbox-close { position: absolute; top: -18px; right: -18px; width: 46px; height: 46px; border: 0; border-radius: 50%; background: #ffffff; color: var(--navy); font-family: Poppins, Arial, sans-serif; font-size: 28px; line-height: 1; font-weight: 700; cursor: pointer; box-shadow: 0 16px 34px rgba(0, 0, 0, 0.28); display: flex; align-items: center; justify-content: center; transition: transform 0.2s ease, background 0.2s ease, color 0.2s ease; }\n    .ols-image-lightbox-close:hover { transform: scale(1.08); background: var(--blue); color: #ffffff; }\n    @media (max-width: 760px) { .ols-zoom-card { border-radius: 22px !important; overflow: hidden !important; } .ols-zoom-card-image { min-height: auto !important; padding: 12px !important; overflow: hidden !important; border-top-left-radius: 22px !important; border-top-right-radius: 22px !important; } .ols-zoom-card img.ols-zoomable-img, .ols-zoom-card img.ols-zoomable-img:hover { transform: none !important; box-shadow: none !important; } .ols-zoom-card-caption { border-bottom-left-radius: 22px !important; border-bottom-right-radius: 22px !important; } .ols-image-lightbox { padding: 16px; } .ols-image-lightbox-inner { width: 100%; max-height: 88vh; } .ols-image-lightbox-img { max-height: 88vh; border-radius: 16px; } .ols-image-lightbox-close { top: 10px; right: 10px; width: 42px; height: 42px; font-size: 26px; } }\n\n\n    .ols-table-wrap { overflow: hidden; border-radius: 22px; border: 1px solid var(--border); background: #ffffff; margin-top: 18px; }\n    .ols-table { width: 100%; border-collapse: collapse; table-layout: fixed; }\n    .ols-table th { background: var(--navy); color: #ffffff; padding: 16px; text-align: left; font-size: clamp(14px, 1.2vw, 17px); font-weight: 600; overflow-wrap: anywhere; }\n    .ols-table td { padding: 16px; border-bottom: 1px solid var(--border); font-size: clamp(14px, 1.15vw, 16px); line-height: 1.45; color: var(--body-text); vertical-align: top; overflow-wrap: anywhere; }\n    .ols-table tr:last-child td { border-bottom: none; }\n\n    .ols-h5p-card { background: linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%); }\n    .ols-h5p-frame { margin-top: 22px; padding: 18px; border-radius: 24px; background: #ffffff; border: 1px solid var(--border); box-shadow: inset 0 0 0 1px rgba(28, 36, 75, 0.03); }\n\n    .ols-faq-list { display: grid; gap: 14px; margin-top: 18px; }\n    .ols-faq-item { background: #ffffff; border: 1px solid var(--border); border-radius: 18px; padding: 18px 20px; box-shadow: var(--inner-shadow); }\n    .ols-faq-item h3 { margin: 0 0 8px; font-size: 20px; line-height: 1.3; color: var(--navy); }\n    .ols-faq-item p { margin: 0; font-size: 16px; line-height: 1.65; color: var(--body-text); }\n\n    .ols-related-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin-top: 18px; }\n    .ols-related-item { border: 1px solid var(--border); border-radius: 18px; padding: 18px; background: #ffffff; color: var(--navy); text-decoration: none; font-weight: 600; line-height: 1.5; transition: transform 0.2s ease, box-shadow 0.2s ease; }\n    .ols-related-item:hover { transform: translateY(-2px); box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08); }\n\n    .ols-course-cta-covalent {\n      width: 100%;\n      margin: 30px 0 24px;\n      font-family: Poppins, Arial, sans-serif;\n    }\n    .ols-course-cta-covalent, .ols-course-cta-covalent * { box-sizing: border-box; }\n    .ols-course-cta-card {\n      overflow: hidden;\n      border-radius: 30px;\n      border: 1px solid var(--border);\n      background: radial-gradient(circle at top left, rgba(37, 99, 235, 0.16), transparent 34%), linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      box-shadow: var(--shadow);\n      padding: 30px;\n    }\n    .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    .ols-course-cta-image-link { display: block; text-decoration: none; border-radius: 24px; }\n    .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    .ols-course-cta-image img { width: 100%; height: auto; display: block; transition: transform 0.45s ease; }\n    .ols-course-cta-image-link:hover .ols-course-cta-image { transform: translateY(-8px) scale(1.015); box-shadow: 0 26px 60px rgba(28, 36, 75, 0.18), 0 0 0 1px rgba(37, 99, 235, 0.12); }\n    .ols-course-cta-image-link:hover .ols-course-cta-image img { transform: scale(1.03); }\n    .ols-course-cta-header-row { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 14px; margin-bottom: 18px; }\n    .ols-course-cta-kicker { display: inline-flex; align-items: center; padding: 8px 14px; border-radius: 999px; background: #ffffff; border: 1px solid rgba(37, 99, 235, 0.18); color: var(--blue); font-size: 14px; line-height: 1.2; font-weight: 700; box-shadow: var(--inner-shadow); }\n    .ols-course-cta-covalent h2 { margin: 0 0 14px; font-size: clamp(28px, 3.5vw, 42px); line-height: 1.15; font-weight: 800; letter-spacing: -0.03em; color: #111827; }\n    .ols-course-cta-intro { margin: 0 0 24px; color: var(--body-text); font-size: clamp(16px, 1.4vw, 18px); line-height: 1.7; font-weight: 300; }\n    .ols-course-cta-features { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; margin: 0 0 30px; }\n    .ols-course-feature { background: rgba(255, 255, 255, 0.78); border: 1px solid var(--border); border-radius: 18px; padding: 16px 18px; }\n    .ols-course-feature h3 { margin: 0 0 6px; color: var(--navy); font-size: 18px; line-height: 1.3; font-weight: 800; }\n    .ols-course-feature p { margin: 0; color: var(--body-text); font-size: 15px; line-height: 1.6; font-weight: 300; }\n    .ols-course-cta-bottom { display: flex; justify-content: center; padding-top: 22px; border-top: 1px solid var(--border); }\n    .ols-course-button { display: inline-flex; align-items: center; justify-content: center; padding: 15px 28px; border-radius: 999px; background: var(--navy); color: #ffffff; text-decoration: none; font-size: 16px; line-height: 1.2; font-weight: 800; box-shadow: 0 12px 26px rgba(28, 36, 75, 0.18); transition: transform 0.2s ease, background 0.2s ease, box-shadow 0.2s ease; }\n    .ols-course-button:hover { transform: translateY(-2px); background: var(--blue); color: #ffffff; box-shadow: 0 16px 32px rgba(37, 99, 235, 0.24); }\n    .ols-course-button-top { flex-shrink: 0; padding: 12px 22px; font-size: 15px; }\n\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    .ols-attribution-card, .ols-attribution-card * { box-sizing: border-box; }\n    .ols-attribution-card p { margin: 0; font-size: 14px; line-height: 1.65; font-weight: 300; color: #667085; }\n    .ols-attribution-card strong { font-weight: 700; color: #1C244B; }\n\n    @media (max-width: 1050px) {\n      .ols-main { max-width: none; }\n      .ols-related-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }\n      .ols-course-cta-top { grid-template-columns: 1fr; }\n      .ols-course-cta-image-link { max-width: 520px; margin: 0 auto; }\n    }\n\n    @media (max-width: 760px) {\n      .ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-card, .ols-faq-card, .ols-attribution-card { padding: 24px 18px; border-radius: 22px; }\n      .ols-note-title { align-items: flex-start; }\n      .ols-related-grid, .ols-course-cta-features { grid-template-columns: 1fr; }\n      .ols-figure-card { border-radius: 22px; }\n      .ols-figure-image { min-height: 210px; padding: 14px; }\n      .ols-figure-caption { padding: 16px; }\n      .ols-table-wrap { border: none; background: transparent; }\n      .ols-table, .ols-table thead, .ols-table tbody, .ols-table th, .ols-table td, .ols-table tr { display: block; width: 100%; }\n      .ols-table { border-collapse: separate; border-spacing: 0; }\n      .ols-table thead { display: none; }\n      .ols-table tr { margin-bottom: 14px; border: 1px solid var(--border); border-radius: 18px; overflow: hidden; background: #ffffff; box-shadow: var(--inner-shadow); }\n      .ols-table td { border-bottom: 1px solid var(--border); padding: 14px 16px; overflow-wrap: anywhere; }\n      .ols-table td:last-child { border-bottom: 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border-radius: 22px; padding: 14px; margin: 18px 0 6px; }\n    .ols-figure-placeholder .ols-figure-caption p { margin: 10px 0 0; font-size: 14px; color: #667085; text-align: center; }\n\n    \/* inline checks (H5P re-flow, Sep 2026) *\/\n    .ols-h5p-card.ols-h5p-inline { padding: 26px 28px; border-left: 6px solid #7c3aed; }\n    .ols-h5p-card.ols-h5p-inline h2 { font-size: clamp(20px, 2.2vw, 27px); letter-spacing: -0.02em; }\n    .ols-h5p-card.ols-h5p-inline > p { margin: 8px 0 0; }\n    .ols-h5p-card.ols-h5p-inline .ols-h5p-frame { margin-top: 16px; padding: 14px; border-radius: 20px; }\n    .ols-h5p-kicker { display: inline-block; margin-bottom: 10px; padding: 5px 12px; border-radius: 999px; background: #ede9fe; color: #5b21b6; font-size: 12px; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; }\n    .ols-h5p-card.ols-h5p-recap { border-left-color: #c9973a; background: linear-gradient(135deg, #ffffff 0%, #fff8e8 100%); }\n    .ols-h5p-recap .ols-h5p-kicker { background: #fdf0d2; color: #8a5a00; }\n    @media (max-width: 760px) { .ols-h5p-card.ols-h5p-inline { padding: 20px 16px; } }\n<\/style>\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>A Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Topic 26 Reaction Kinetics<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/\">Topic 26 Reaction Kinetics Overview<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-equations-orders-and-the-rate-constant\/\">Rate Equations, Orders and the Rate Constant<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/techniques-for-measuring-rates\/\">Techniques for Measuring Rates<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/concentration-time-graphs-and-half-life\/\">Concentration\u2013Time Graphs and Half-Life<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-concentration-graphs-and-the-initial-rates-method\/\">Rate\u2013Concentration Graphs and the Initial-Rates Method<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/the-iodine-propanone-reaction\/\">The Iodine\u2013Propanone Reaction<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-determining-step-and-reaction-mechanisms\/\">Rate-Determining Step and Reaction Mechanisms<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/\">Activation Energy and the Arrhenius Equation<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/heterogeneous-and-homogeneous-catalysis\/\">Heterogeneous and Homogeneous Catalysis<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Other Sections<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-8-reaction-kinetics\/\">Topic 8 Reaction Kinetics (AS)<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-7-equilibria\/\">Topic 7 Equilibria<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-5-chemical-energetics\/\">Topic 5 Chemical Energetics<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/\">Practical Skills<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\n\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() 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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\/cie\/\">Cambridge International (CIE)<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/\">Topic 26 Reaction Kinetics<\/a> \/\n<span>Heterogeneous and Homogeneous Catalysis<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Heterogeneous and Homogeneous Catalysis<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to the two kinds of catalyst: a solid heterogeneous catalyst providing a surface for a gas-phase reaction (adsorption, bond weakening, reaction and desorption, as in the Haber process and the catalytic converter) and a homogeneous catalyst used in one step and regenerated in a later one, with the Fe\u00b2\u207a\/Fe\u00b3\u207a and NO\u2082 examples.<\/p>\n\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">A Level<\/div>\n<div class=\"ols-badge\">Topic 26: Reaction Kinetics<\/div>\n<div class=\"ols-badge\">9701 Paper 4<\/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:<br><span>Dr. Mohammed Al-Fatah<\/span>\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        <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        View LinkedIn Profile\n      <\/a>\n\n    <\/div>\n\n  <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>Two Kinds of Catalyst<\/h2>\n<\/div>\n<p>A <strong>catalyst<\/strong> increases the rate of a reaction by providing an <strong>alternative route with a lower activation energy<\/strong>. It is chemically unchanged at the end because it is regenerated.<\/p><p>With a lower E\u2090 a larger fraction of collisions have enough energy to react, so the rate constant is larger at the same temperature. Catalysts are sorted by their phase relative to the reactants.<\/p>\n<div class=\"ols-table-wrap\"><table class=\"ols-table\"><thead><tr><th>Type<\/th><th>Phase<\/th><th>Examples<\/th><th>How it works<\/th><\/tr><\/thead><tbody><tr><td><strong>Homogeneous catalyst<\/strong><\/td><td>It is in the <strong>same phase<\/strong> as the reactants.<\/td><td>An acid catalysing a reaction in aqueous solution, or a gas catalysing a reaction between gases.<\/td><td>It works by reacting with a reactant to form an intermediate, which then breaks down to give the product and release the catalyst.<\/td><\/tr><tr><td><strong>Heterogeneous catalyst<\/strong><\/td><td>It is in a <strong>different phase<\/strong> from the reactants.<\/td><td>Almost always a solid catalysing a reaction between gases or in solution.<\/td><td>It works by providing a surface on which the reaction takes place.<\/td><\/tr><\/tbody><\/table><\/div>\n<div class=\"ols-key-box\">\n<p><strong>Definition:<\/strong> Homogeneous catalyst: in the same phase as the reactants. Heterogeneous catalyst: in a different phase from the reactants, usually a solid with gaseous or dissolved reactants.<\/p>\n<\/div>\n<div class=\"ols-zoom-card\">\n<div class=\"ols-zoom-card-image\">\n<a class=\"ols-lightbox-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/t11x-catalysttypes.jpg\" aria-label=\"Open image full screen\">\n<img decoding=\"async\" class=\"ols-zoomable-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/t11x-catalysttypes.jpg\" alt=\"Two-column poster comparing homogeneous and heterogeneous catalysts by phase, mechanism and examples.\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>A homogeneous catalyst is in the same phase as the reactants and a heterogeneous catalyst is in a different phase, but both provide a route with a lower activation energy and are regenerated.<\/p><\/div>\n<\/div>\n<\/article>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>How a Solid Catalyst Works<\/h2>\n<\/div>\n<p>The reaction takes place on the <strong>surface<\/strong> of the solid, at particular positions called <strong>active sites<\/strong>. Four things happen in turn:<\/p>\n<ol><li><strong>Adsorption:<\/strong> reactant molecules from the gas phase form weak bonds to the atoms of the surface. This holds them close together in a favourable orientation, and it concentrates them at the surface.<\/li><li><strong>Bond weakening:<\/strong> the bonds within the adsorbed molecules are stretched and weakened, and can break, because the electrons in them are partly shared with the surface. The activation energy for reaction is lower than in the gas phase.<\/li><li><strong>Reaction:<\/strong> the adsorbed atoms or fragments move across the surface and form new bonds with each other.<\/li><li><strong>Desorption:<\/strong> the product molecule breaks away from the surface, freeing the active site for the next reactants.<\/li><\/ol>\n<p>The classic example is <strong>iron in the Haber process<\/strong>. Nitrogen and hydrogen adsorb on the iron, the strong N\u2261N and H\u2013H bonds are weakened and broken, hydrogen atoms add to nitrogen atoms one at a time, and the ammonia formed desorbs.<\/p><p>In a car&#8217;s <strong>catalytic converter<\/strong>, a thin layer of platinum, palladium and rhodium on a ceramic honeycomb catalyses the reaction between the two main pollutants, 2CO + 2NO \u2192 2CO\u2082 + N\u2082, so that harmful carbon monoxide and nitrogen monoxide leave as carbon dioxide and nitrogen.<\/p><p>The honeycomb gives a very large surface area for a small mass of expensive metal.<\/p>\n<p>The <strong>strength of adsorption<\/strong> has to be right. If the bonds to the surface are too strong, as with tungsten, the products cannot desorb and the active sites are blocked.<\/p><p>If they are too weak, as with silver, the reactants do not stay long enough for their bonds to be weakened. Nickel, platinum and the other metals in the middle of the d block adsorb strongly enough to activate reactants but weakly enough to release products.<\/p><p>A catalyst is <strong>poisoned<\/strong> when an impurity such as sulfur or lead adsorbs so strongly that it blocks the active sites permanently.<\/p><p>This is why leaded petrol destroys catalytic converters and why the feed gases for the Haber process are cleaned of sulfur compounds first.<\/p>\n<!-- 3D card: haber-catalysis (30 Sep 2026, reused) -->\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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right:14px; transform:none; font-size:11px; padding:6px 10px;}\n}\n\/* on a phone the caption needs the full top row, so the drag hint goes *\/\n@media (max-width:480px){\n  .ols-hab-001 .hab-hint{display:none;}\n}\n@media (prefers-reduced-motion:reduce){\n  .ols-hab-001 .hab-seg button,.ols-hab-001 .hab-pill{transition:none;}\n}\n\n.ols-cc-hab-001{\n  font-family:'Poppins',system-ui,-apple-system,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;\n  margin:10px auto 0; text-align:center; font-size:11px; font-style:italic; color:#aab0c0;\n}\n.ols-cc-hab-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-hab-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"hab-head\">\n  <h2 class=\"hab-title\">Heterogeneous Catalysis on an Iron Surface<\/h2>\n  <p class=\"hab-sub\">Follow nitrogen and hydrogen through the Haber process on iron: adsorption, bond breaking, reaction on the surface and desorption of ammonia.<\/p>\n<\/div>\n\n<div class=\"hab-stage\" id=\"habStage\">\n  <canvas class=\"hab-canvas\" id=\"habCanvas\"><\/canvas>\n  <div class=\"hab-overlay\" id=\"habOverlay\"><\/div>\n  <div class=\"hab-caption\" id=\"habCaption\"><\/div>\n  <div class=\"hab-hint\" id=\"habHint\">Drag to rotate<\/div>\n  <div class=\"hab-badges\" id=\"habBadges\"><\/div>\n<\/div>\n\n<div class=\"hab-controls\">\n  <div class=\"hab-row\">\n    <span class=\"hab-rowlab\">Step<\/span>\n    <div class=\"hab-seg\" role=\"group\" aria-label=\"Step\">\n      <button type=\"button\" data-step=\"1\" aria-pressed=\"true\">Adsorb<\/button>\n      <button type=\"button\" data-step=\"2\" aria-pressed=\"false\">Weaken<\/button>\n      <button type=\"button\" data-step=\"3\" aria-pressed=\"false\">React<\/button>\n      <button type=\"button\" data-step=\"4\" aria-pressed=\"false\">Desorb<\/button>\n      <button type=\"button\" data-step=\"5\" aria-pressed=\"false\">Promoter<\/button>\n      <button type=\"button\" data-step=\"6\" aria-pressed=\"false\">Poison<\/button>\n    <\/div>\n  <\/div>\n\n  <div class=\"hab-row\">\n    <span class=\"hab-rowlab\">View<\/span>\n    <button type=\"button\" class=\"hab-pill\" id=\"habResetV\">Reset view<\/button>\n  <\/div>\n<\/div>\n\n<div class=\"hab-info\">\n  <h3 id=\"habInfoTitle\"><\/h3>\n  <p id=\"habInfoText\"><\/p>\n  <div class=\"hab-facts\" id=\"habFacts\"><\/div>\n  <div class=\"hab-key\">\n    <span><i style=\"background:#969caa\"><\/i>Iron, Fe<\/span>\n    <span><i style=\"background:#3462c8\"><\/i>Nitrogen<\/span>\n    <span><i style=\"background:#eef0f5\"><\/i>Hydrogen<\/span>\n    <span><i style=\"background:#8f40d4\"><\/i>Potassium promoter<\/span>\n    <span><i style=\"background:#bfa6a6\"><\/i>Aluminium oxide promoter<\/span>\n    <span><i style=\"background:#dcbe28\"><\/i>Sulfur poison<\/span>\n    <span><i style=\"background:#ffffff; border:2px solid #2f9e57; border-radius:50%\"><\/i>Free active site<\/span>\n    <span><i style=\"background:#ffffff; border:2px solid #d9433a; border-radius:50%\"><\/i>Blocked site<\/span>\n    <span><i style=\"background:#e83c34\"><\/i>Bond breaking<\/span>\n    <span><i style=\"background:#38b258\"><\/i>Bond forming<\/span>\n    <span><i style=\"background:#ffffff; border:1.5px dashed rgba(28,36,75,0.7)\"><\/i>Bond to the surface<\/span>\n  <\/div>\n<\/div>\n<\/section>\n\n<p class=\"ols-cc-hab-001\">&copy; Dr. Mohammed Al-Fatah &#8211; <a href=\"https:\/\/www.onlinelearningsystem.net\" target=\"_blank\" rel=\"noopener\">onlinelearningsystem.net<\/a><\/p>\n<script src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/JS\/haber-catalysis.js?v=20261003e\"><\/script>\n<div class=\"ols-key-box\">\n<p><strong>Exam wording:<\/strong> &#8220;Reactants adsorb onto active sites on the surface; bonds in the reactants are weakened, lowering the activation energy; the atoms react on the surface; the products desorb.&#8221;<\/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>Check: Reaction at a Surface<\/h2>\n<p>Put the steps at a catalyst surface in order and explain them for reactions not used on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1096\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>How a Homogeneous Catalyst Works<\/h2>\n<\/div>\n<p>A homogeneous catalyst takes part in the mechanism: it is <strong>used up in one step<\/strong> and <strong>regenerated in a later step<\/strong>.<\/p><p>Because it comes out unchanged, it does not appear in the overall equation, and a small amount can catalyse a large amount of reaction.<\/p><p>The route through the catalyst has a lower activation energy than the direct route. Its reaction profile shows two smaller humps with the intermediate in the dip between them.<\/p>\n<p><strong>Fe\u00b2\u207a and the peroxodisulfate\u2013iodide reaction.<\/strong> Peroxodisulfate ions oxidise iodide ions: S\u2082O\u2088\u00b2\u207b + 2I\u207b \u2192 2SO\u2084\u00b2\u207b + I\u2082.<\/p><p>The uncatalysed reaction is slow because it needs a collision between <strong>two negative ions<\/strong>, which repel each other, so the activation energy is high.<\/p><p>Adding Fe\u00b2\u207a replaces it with two fast steps, each between a positive ion and a negative ion:<\/p>\n<p style=\"text-align:center\">stage 1: S\u2082O\u2088\u00b2\u207b + 2Fe\u00b2\u207a \u2192 2SO\u2084\u00b2\u207b + 2Fe\u00b3\u207a<br>stage 2: 2Fe\u00b3\u207a + 2I\u207b \u2192 2Fe\u00b2\u207a + I\u2082<\/p>\n<p>The Fe\u00b2\u207a used in stage 1 is re-formed in stage 2. Adding the stages cancels the iron ions and gives the overall equation.<\/p><p><strong>Fe\u00b3\u207a works just as well<\/strong>, because the stages simply run in the other order: Fe\u00b3\u207a oxidises iodide first, and the Fe\u00b2\u207a formed is then re-oxidised by peroxodisulfate.<\/p><p>This is why transition-metal ions with two accessible oxidation states make good homogeneous catalysts.<\/p>\n<p><strong>Oxides of nitrogen and sulfur dioxide.<\/strong> In the atmosphere, sulfur dioxide from burning fossil fuels is oxidised only slowly by oxygen, but nitrogen dioxide from car engines catalyses it in two steps:<\/p>\n<p style=\"text-align:center\">step 1: SO\u2082 + NO\u2082 \u2192 SO\u2083 + NO<br>step 2: NO + \u00bdO\u2082 \u2192 NO\u2082<\/p>\n<p>The NO\u2082 consumed in the first step is regenerated in the second, and the sum is the overall reaction SO\u2082 + \u00bdO\u2082 \u2192 SO\u2083.<\/p><p>The sulfur trioxide dissolves in water droplets to give sulfuric acid, so a little NO\u2082 produces a great deal of acid rain: it is a catalyst, not a reactant.<\/p><div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> for each example you should be able to write the two steps, show that they add up to the overall equation, and say which species is the catalyst and why: it is used in the first step and re-formed in the second.<\/p><\/div>\n<div class=\"ols-zoom-card\">\n<div class=\"ols-zoom-card-image\">\n<a class=\"ols-lightbox-link\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/kinetics-t11-08-homogeneous-catalysis.jpg\" aria-label=\"Open image full screen\">\n<img decoding=\"async\" class=\"ols-zoomable-img ols-lightbox-target\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/09\/kinetics-t11-08-homogeneous-catalysis.jpg\" alt=\"Homogeneous catalysis cycles: Fe\u00b2\u207a catalysing the reaction of peroxodisulfate with iodide, and NO\u2082 catalysing the oxidation of SO\u2082\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>Two homogeneous catalytic cycles: Fe\u00b2\u207a\/Fe\u00b3\u207a in the peroxodisulfate\u2013iodide reaction and NO\u2082\/NO in the oxidation of sulfur dioxide, the catalyst regenerated in each.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Homogeneous catalyst: used in one step, regenerated in a later step, so it is absent from the overall equation. Look for the species that is a reactant in one step and a product in another.<\/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>Check: Catalytic Cycles<\/h2>\n<p>Identify the catalyst and the intermediate in two-step mechanisms not shown on this page, and explain why the catalysed route is faster.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1097\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Say<\/h3><p>&#8220;A heterogeneous catalyst is in a different phase from the reactants and provides a surface: adsorption, bond weakening, reaction, desorption.&#8221; &#8220;A homogeneous catalyst is used in one step and regenerated in a later step.&#8221; &#8220;The catalyst provides an alternative route with a lower activation energy.&#8221;<\/p>\n<h3>Do not say<\/h3><p>&#8220;The catalyst lowers the activation energy of the reaction&#8221; (it provides a different route with a lower E\u2090). &#8220;Absorbed&#8221; for adsorbed. &#8220;The catalyst is used up.&#8221;<\/p>\n<h3>Watch for<\/h3><p>Being asked why the uncatalysed peroxodisulfate\u2013iodide reaction is slow (two negative ions must collide) or why Fe\u00b3\u207a also catalyses it (the two stages run in the other order). Being asked to add two steps and show that the catalyst cancels.<\/p>\n<\/article>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Use these quick answers to check the catalysis ideas.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>What is the difference between adsorption and absorption?<\/h3>\n<p>Adsorption is bonding to a surface: the reactant molecules attach to the outside of the solid catalyst. Absorption would mean being taken into the bulk of the solid. Heterogeneous catalysis is a surface process, so the word is adsorption.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why does adsorption speed up the reaction?<\/h3>\n<p>Bonding to the surface weakens the bonds within the adsorbed molecules, holds them close together in a favourable orientation, and so lowers the activation energy of the reaction. The products are then desorbed, freeing the surface.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why is a catalyst that adsorbs too strongly no good?<\/h3>\n<p>If the products stay bound to the surface they block the active sites and nothing else can be adsorbed, so the catalyst is poisoned. Too weak an adsorption is also useless, because the reactants do not stay on the surface long enough to react.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>How can a homogeneous catalyst appear in the mechanism but not in the overall equation?<\/h3>\n<p>It is used up in one step and regenerated in a later one, so it cancels when the steps are added. The catalysed route usually has two steps with a lower activation energy each, in place of one slow uncatalysed step.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why can Fe\u00b2\u207a or Fe\u00b3\u207a catalyse the reaction between I\u207b and S\u2082O\u2088\u00b2\u207b?<\/h3>\n<p>The uncatalysed reaction is between two negative ions, which repel each other, so the activation energy is high. Fe\u00b3\u207a oxidises I\u207b to I\u2082 and is reduced to Fe\u00b2\u207a, which then reduces S\u2082O\u2088\u00b2\u207b and is turned back into Fe\u00b3\u207a; each step is between oppositely charged ions and is fast.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section class=\"ols-related-card\">\n<h2>Related Topic 26 Reaction Kinetics Pages<\/h2>\n<p>Use these pages to connect the ideas across Topic 26 Reaction Kinetics and the rest of the course.<\/p>\n<div class=\"ols-related-grid\">\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-equations-orders-and-the-rate-constant\/\">Rate Equations, Orders and the Rate Constant<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/techniques-for-measuring-rates\/\">Techniques for Measuring Rates<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/concentration-time-graphs-and-half-life\/\">Concentration\u2013Time Graphs and Half-Life<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-concentration-graphs-and-the-initial-rates-method\/\">Rate\u2013Concentration Graphs and the Initial-Rates Method<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/the-iodine-propanone-reaction\/\">The Iodine\u2013Propanone Reaction<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-determining-step-and-reaction-mechanisms\/\">Rate-Determining Step and Reaction Mechanisms<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/\">Activation Energy and the Arrhenius Equation<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/\">Topic 26 Reaction Kinetics Overview<\/a>\n<\/div>\n<\/section>\n<section class=\"ols-attribution-card\">\n        <p><strong>Copyright and author footprint:<\/strong> This OLS revision page was written for Online Learning System by <strong>Dr. Mohammed Al-Fatah<\/strong>. It is designed for A Level Chemistry revision and should not be copied or redistributed without permission.<\/p>\n      <\/section>\n\n      <div class=\"ols-image-lightbox\" id=\"olsImageLightboxNatureCovalentBonding9ch0\" aria-hidden=\"true\" role=\"dialog\" aria-modal=\"true\" aria-label=\"Expanded revision image\">\n        <div class=\"ols-image-lightbox-inner\">\n          <button class=\"ols-image-lightbox-close\" type=\"button\" aria-label=\"Close enlarged image\">\u00d7<\/button>\n          <img decoding=\"async\" class=\"ols-image-lightbox-img\" src=\"\" alt=\"\">\n        <\/div>\n      <\/div>\n\n      <script>\n        (function(){\n          var page = document.querySelector(\".ols-nature-of-covalent-bonding-9ch0-page\");\n          if (!page) { return; }\n          var lightbox = page.querySelector(\"#olsImageLightboxNatureCovalentBonding9ch0\");\n          if (!lightbox) { return; }\n          var lightboxImage = lightbox.querySelector(\".ols-image-lightbox-img\");\n    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