{"id":11567,"date":"2026-09-28T14:13:07","date_gmt":"2026-09-28T13:13:07","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/redox-titrations-manganate-vii-and-iodine-thiosulfate\/"},"modified":"2026-10-03T08:38:13","modified_gmt":"2026-10-03T07:38:13","slug":"redox-titrations-manganate-vii-and-iodine-thiosulfate","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/redox-titrations-manganate-vii-and-iodine-thiosulfate\/","title":{"rendered":"Redox Titrations: Manganate(VII) and Iodine\u2013Thiosulfate"},"content":{"rendered":"<script src=\"https:\/\/cdnjs.cloudflare.com\/ajax\/libs\/three.js\/r128\/three.min.js\"><\/script>\n\n<section class=\"ols-revision-page ols-core-practical-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      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n\n    .ols-revision-page * { box-sizing: border-box; }\n    .ols-main { min-width: 0; max-width: 970px; }\n    .ols-breadcrumbs { display: flex; flex-wrap: wrap; gap: 8px; margin: 10px 0 22px; font-size: 15px; color: var(--grey-text); }\n    .ols-breadcrumbs a, .ols-breadcrumbs span { color: var(--grey-text); text-decoration: none; font-weight: 600; }\n    .ols-breadcrumbs a:hover { color: var(--blue); text-decoration: underline; text-underline-offset: 3px; }\n    .ols-title-card, .ols-note-card, .ols-h5p-card, .ols-related-card, .ols-faq-card { background: #ffffff; border: 1px solid var(--border); border-radius: 28px; box-shadow: var(--shadow); padding: 34px; margin-bottom: 24px; overflow: hidden; }\n    .ols-title-card { background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%); }\n    .ols-title-card h1 { margin: 0 0 18px; font-size: clamp(36px, 5vw, 58px); line-height: 1.08; font-weight: 800; letter-spacing: -0.04em; color: #111827; }\n    .ols-page-intro { font-size: 19px; line-height: 1.7; font-weight: 300; color: var(--body-text); margin: 0 0 22px; }\n    .ols-badges { display: flex; flex-direction: column; align-items: flex-start; gap: 12px; margin-bottom: 22px; }\n    .ols-badge { display: inline-flex; align-items: center; padding: 9px 14px; border-radius: 999px; background: #ffffff; border: 1px solid var(--border); font-size: 15px; font-weight: 600; color: var(--navy); }\n    .ols-author { display: flex; align-items: center; gap: 20px; padding: 28px; border-radius: 28px; background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%); border: 1px solid rgba(28,36,75,0.12); box-shadow: 0 18px 45px rgba(28,36,75,0.10); margin-top: 22px; }\n    .ols-author-avatar-img { 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; 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}\n      .ols-course-cta-card { padding: 20px; border-radius: 24px; }\n      .ols-course-cta-header-row { align-items: stretch; }\n      .ols-course-button-top, .ols-course-button { width: 100%; }\n    }\n  \n    .ols-figure-placeholder .ols-placeholder-box { border: 2px dashed #c9973a; background: #fffaf0; border-radius: 16px; padding: 26px 22px; font-weight: 700; color: #7a4b12; text-align: center; line-height: 1.6; }\n    .ols-figure-placeholder .ols-figure-image { background: transparent; }\n    .ols-figure-placeholder { background: #ffffff; border: 1px solid rgba(28, 36, 75, 0.12); border-radius: 22px; padding: 14px; margin: 18px 0 6px; }\n    .ols-figure-placeholder .ols-figure-caption p { margin: 10px 0 0; font-size: 14px; color: #667085; text-align: center; }\n\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\n    \/* core practical pages (Sep 2026) *\/\n    .ols-note-card h3 { margin: 22px 0 8px; font-size: 18px; line-height: 1.25; font-weight: 500; color: var(--navy); }\n    .ols-table td { overflow-wrap: anywhere; }\n<\/style>\n\n  <aside class=\"ols-sidebar\">\n  <div class=\"ols-sidebar-header\">\n    <h3>Revision Notes<\/h3>\n    <p>Cambridge International AS Level Chemistry<\/p>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Practical Skills (Paper 3)<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/molar-volume-of-a-gas\/\">Gas collection: Molar Volume of a Gas<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/enthalpy-change-via-hess-law\/\">Thermometry: Enthalpy Change via Hess's Law<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/concentration-of-hcl-by-titration\/\">Titration: Concentration of HCl by Titration<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/preparation-of-a-standard-solution\/\">Standard solution: Preparation of a Standard Solution<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/rates-of-hydrolysis-of-halogenoalkanes\/\">Hydrolysis rates: Hydrolysis of Halogenoalkanes<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/preparing-an-organic-liquid-chlorination-of-2-methylpropan-2-ol\/\">Organic prep: Chlorination of 2-methylpropan-2-ol<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/oxidation-of-an-alcohol-distillation-and-reflux\/\">Distil or reflux: Oxidation of an Alcohol<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/qualitative-analysis-of-inorganic-and-organic-unknowns\/\">Qualitative analysis: Analysis of Inorganic and Organic Unknowns<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/rates-of-reaction-timing-an-observation\/\">Rates: Rates of Reaction<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/gravimetric-analysis-water-of-crystallisation\/\">Gravimetric: Gravimetric and Composition Analysis<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/redox-titrations-manganate-vii-and-iodine-thiosulfate\/\">Redox titrations: Redox Titrations<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n\n  <div class=\"ols-topic-group\">\n    <h4>Useful Links<\/h4>\n\n    <ul class=\"ols-topic-list\">\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/\">Cambridge International (CIE) Chemistry<\/a>\n      <\/li>\n      <li>\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/\">Practical Skills (Paper 3)<\/a>\n      <\/li>\n    <\/ul>\n  <\/div>\n<\/aside>\n\n<script>\ndocument.addEventListener('DOMContentLoaded', function () {\n  var currentPath = window.location.pathname.replace(\/\\\/$\/, '');\n  var sidebarLinks = document.querySelectorAll('.ols-sidebar .ols-topic-list a');\n  sidebarLinks.forEach(function (link) {\n    var linkPath = new URL(link.href, window.location.origin).pathname.replace(\/\\\/$\/, '');\n    if (linkPath === currentPath) { link.closest('li').classList.add('active'); } else { link.closest('li').classList.remove('active'); }\n  });\n});\n<\/script>\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/\">Cambridge International (CIE)<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/\">Practical Skills (Paper 3)<\/a> \/\n<span>Redox Titrations: Manganate(VII) and Iodine\u2013Thiosulfate<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Redox Titrations: Manganate(VII) and Iodine\u2013Thiosulfate<\/h1>\n        <p class=\"ols-page-intro\">A focused revision guide to redox titrations for Cambridge International A Level Chemistry: potassium manganate(VII) with iron(II), hydrogen peroxide and ethanedioate, the choice of acid, the self-indicating end point, iodine\u2013thiosulfate titrations with starch, and the calculations from half-equations.<\/p>\n\n        <div class=\"ols-badges\">\n<div class=\"ols-badge\">AS Level<\/div>\n<div class=\"ols-badge\">Practical Skills: Redox Titrations<\/div>\n<div class=\"ols-badge\">9701 Paper 3<\/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\">Chemistry specialist revision notes for Cambridge International AS and A Level Chemistry.<\/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      <section class=\"ols-h5p-card ols-h5p-inline ols-h5p-recap\">\n<span class=\"ols-h5p-kicker\">Before you start<\/span>\n<h2>Before You Start: Oxidation Numbers and Half-Equations<\/h2>\n<p>Three quick questions on the redox ideas this practical builds on: oxidation numbers, balancing a half-equation and naming the oxidising agent.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1055\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">1<\/div>\n<h2>What This Practical Is Testing<\/h2>\n<\/div>\n<p>This practical, Practical Skills: Redox Titrations on the Cambridge International course, finds the concentration of a <strong>reducing agent<\/strong> or an <strong>oxidising agent<\/strong> by titration.<\/p><p>The practical paper names two families. Potassium manganate(VII) is titrated with <strong>hydrogen peroxide, iron(II) ions or ethanedioic acid (or its salts)<\/strong>, and sodium thiosulfate is titrated with <strong>iodine<\/strong>.<\/p><p>The burette technique, the rough titration and the rule for concordant titres (within 0.10 cm\u00b3 of each other) are the same as in <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/concentration-of-hcl-by-titration\/\">Practical Skills: Titration (concentration of hcl by titration)<\/a> and <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/preparation-of-a-standard-solution\/\">Practical Skills: Standard Solutions (preparation of a standard solution)<\/a>.<\/p><p>What is new is the chemistry of the end point and the mole ratio, which comes from the balanced redox equation.<\/p>\n<p>On the Cambridge International course this practical is examined through Paper 3, a timed laboratory examination that assesses manipulation, observation, presentation of data, analysis and evaluation.<\/p><p>Questions ask you to write or use half-equations (syllabus 6.1, oxidation numbers and balancing by changes in oxidation number), to calculate a concentration or a percentage purity from a mean titre (2.4.1).<\/p><p>They also ask you to describe and explain the end point, and to explain the choice of acid.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> In a redox titration the mole ratio comes from the balanced redox equation: 1 MnO\u2084\u207b reacts with 5 Fe\u00b2\u207a; 2 MnO\u2084\u207b with 5 H\u2082O\u2082 or 5 C\u2082O\u2084\u00b2\u207b; 2 S\u2082O\u2083\u00b2\u207b with 1 I\u2082.<\/p>\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>Safety and Apparatus<\/h2>\n<\/div>\n<p>The glassware is the same as for an acid\u2013base titration; the reagents bring their own hazards and handling rules.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Item<\/th><th>What it is for<\/th><th>Precision or note<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>50 cm\u00b3 burette<\/strong><\/td><td>Delivers the titrant: KMnO\u2084(aq) or Na\u2082S\u2082O\u2083(aq)<\/td><td>\u00b10.05 cm\u00b3 per reading; KMnO\u2084 is read at the top of the meniscus<\/td><\/tr>\n<tr><td><strong>25.0 cm\u00b3 pipette and filler<\/strong><\/td><td>Measures the solution being analysed<\/td><td>\u00b10.06 cm\u00b3<\/td><\/tr>\n<tr><td><strong>250 cm\u00b3 conical flask and white tile<\/strong><\/td><td>Holds the mixture; the tile shows the faint pink or the last trace of blue-black<\/td><td>swirl after each addition<\/td><\/tr>\n<tr><td><strong>10 cm\u00b3 measuring cylinder<\/strong><\/td><td>Adds the excess dilute sulfuric acid, or the excess KI<\/td><td>the amount only has to be in excess, so a cylinder is precise enough<\/td><\/tr>\n<tr><td><strong>Water bath at about 60 \u00b0C<\/strong><\/td><td>Warms ethanedioate solutions before and during the titration<\/td><td>the reaction is too slow at room temperature<\/td><\/tr>\n<tr><td><strong>Starch solution<\/strong><\/td><td>Indicator for iodine, added near the end point<\/td><td>freshly made<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Safety:<\/strong> Potassium manganate(VII) is an oxidising agent and stains skin and clothes. Dilute sulfuric acid (1 mol dm\u207b\u00b3) is an irritant. Iodine solution stains and irritates. Wear eye protection, and take care with the hot water bath when titrating ethanedioate.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">3<\/div>\n<h2>Method: Step by Step<\/h2>\n<\/div>\n<p>The method below is for the titration of iron(II) ions, from ammonium iron(II) sulfate, with potassium manganate(VII). The manganate(VII) is in the burette and no indicator is added.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Step<\/th><th>What you do<\/th><th>Why<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Fill the burette<\/strong><\/td><td>Rinse the burette with the KMnO\u2084(aq), fill it and record the initial reading at the top of the meniscus.<\/td><td>The solution is too dark to see the bottom of the meniscus; reading the same point every time keeps the titre correct.<\/td><\/tr>\n<tr><td><strong>Pipette the sample<\/strong><\/td><td>Pipette 25.0 cm\u00b3 of the iron(II) solution into a conical flask.<\/td><td>An accurately known volume of the solution being analysed.<\/td><\/tr>\n<tr><td><strong>Acidify<\/strong><\/td><td>Add about 10 cm\u00b3 of 1 mol dm\u207b\u00b3 sulfuric acid.<\/td><td>H\u207a is a reactant in the reduction of MnO\u2084\u207b; an excess makes sure Mn\u00b2\u207a forms and not brown MnO\u2082.<\/td><\/tr>\n<tr><td><strong>Rough titration<\/strong><\/td><td>Add the KMnO\u2084(aq) with swirling until the first permanent pale pink colour appears.<\/td><td>Shows roughly where the end point is.<\/td><\/tr>\n<tr><td><strong>Accurate titrations<\/strong><\/td><td>Repeat, adding the KMnO\u2084(aq) dropwise near the end point, and stop at the first pale pink that lasts about 30 s.<\/td><td>One drop of excess MnO\u2084\u207b colours the colourless solution; it is self-indicating.<\/td><\/tr>\n<tr><td><strong>Concordant results<\/strong><\/td><td>Repeat until two titres agree within 0.10 cm\u00b3 of each other, and record every burette reading to the nearest 0.05 cm\u00b3.<\/td><td>Concordant titres show the end point was judged consistently.<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<!-- 3D card: redox (27 Sep 2026) -->\n<!-- Copyright (c) 2026 Dr. Mohammed Al-Fatah, onlinelearningsystem.net. 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width:100%; height:100%; margin:0; border-radius:0; border:0; padding:16px 20px; display:flex; flex-direction:column; overflow:auto;}\n.ols-rdx-001:fullscreen .rdx-head{display:none;}\n.ols-rdx-001:fullscreen .rdx-stage{flex:1 1 auto; height:auto; min-height:320px;}\n.ols-rdx-001:-webkit-full-screen{max-width:none; width:100%; height:100%; margin:0; border-radius:0; border:0; padding:16px 20px; display:flex; flex-direction:column; overflow:auto;}\n.ols-rdx-001:-webkit-full-screen .rdx-head{display:none;}\n.ols-rdx-001:-webkit-full-screen .rdx-stage{flex:1 1 auto; height:auto; min-height:320px;}\n\n.ols-cc-rdx-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-rdx-001 a{color:#aab0c0; text-decoration:none;}\n.ols-cc-rdx-001 a:hover{text-decoration:underline;}\n<\/style>\n\n<div class=\"rdx-head\">\n  <h2 class=\"rdx-title\">Redox Titrations: Manganate(VII) and Iodine\u2013Thiosulfate<\/h2>\n  <p class=\"rdx-sub\">Titrate iron(II) with self-indicating manganate(VII), watch autocatalysis in the ethanedioate titration, then find copper(II) by iodine and thiosulfate with starch added near the end.<\/p>\n<\/div>\n\n<div class=\"rdx-stage\" id=\"rdxStage\" tabindex=\"0\" aria-label=\"Film of the practical. Space plays or pauses, the left and right arrow keys skip 10 seconds.\">\n  <canvas class=\"rdx-canvas\" id=\"rdxCanvas\" aria-hidden=\"true\"><\/canvas>\n  <div class=\"rdx-overlay\" id=\"rdxOverlay\"><\/div>\n  <div class=\"rdx-subt\" id=\"rdxSubt\"><\/div>\n  <div class=\"rdx-hint\" id=\"rdxHint\" hidden>Paused: drag to look around<\/div>\n  <button type=\"button\" class=\"rdx-poster\" id=\"rdxPoster\" aria-label=\"Play the film\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M7 4.5v15l12.5-7.5z\"\/><\/svg><span>Replay<\/span><\/button>\n<\/div>\n\n<div class=\"rdx-player\" id=\"rdxPlayer\" role=\"group\" aria-label=\"Film controls\">\n  <button type=\"button\" class=\"rdx-pb\" id=\"rdxPlay\" aria-label=\"Play\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M7 4.5v15l12.5-7.5z\"\/><\/svg><\/button>\n  <button type=\"button\" class=\"rdx-pb\" id=\"rdxBack\" aria-label=\"Back 10 seconds\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M12 4V1.5L7.5 5 12 8.5V6a7 7 0 1 1-7 7H3a9 9 0 1 0 9-9z\"\/><text x=\"12.2\" y=\"16.2\" text-anchor=\"middle\">10<\/text><\/svg><\/button>\n  <button type=\"button\" class=\"rdx-pb\" id=\"rdxFwd\" aria-label=\"Forward 10 seconds\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M12 4V1.5L16.5 5 12 8.5V6a7 7 0 1 0 7 7h2a9 9 0 1 1-9-9z\"\/><text x=\"11.8\" y=\"16.2\" text-anchor=\"middle\">10<\/text><\/svg><\/button>\n  <button type=\"button\" class=\"rdx-pb\" id=\"rdxRestart\" aria-label=\"Restart\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M5.5 5h2.2v14H5.5zM9.2 12l9.3 6.8V5.2z\"\/><\/svg><\/button>\n  <div class=\"rdx-prog\" id=\"rdxProg\" role=\"slider\" tabindex=\"0\" aria-label=\"Seek\" aria-valuemin=\"0\" aria-valuemax=\"264\" aria-valuenow=\"0\" aria-valuetext=\"0:00\">\n    <div class=\"rdx-track\"><div class=\"rdx-fill\" id=\"rdxFill\"><\/div><\/div>\n    <div class=\"rdx-thumb\" id=\"rdxThumb\"><\/div>\n  <\/div>\n  <span class=\"rdx-time\" id=\"rdxTime\">0:00 \/ 4:24<\/span>\n  <button type=\"button\" class=\"rdx-pb rdx-speed\" id=\"rdxSpeed\" aria-label=\"Playback speed 1\u00d7\">1\u00d7<\/button>\n  <button type=\"button\" class=\"rdx-pb\" id=\"rdxFs\" aria-label=\"Full screen\"><svg viewBox=\"0 0 24 24\" aria-hidden=\"true\"><path d=\"M4 9V4h5v2H6v3zm11-5h5v5h-2V6h-3zM4 15h2v3h3v2H4zm14 3v-3h2v5h-5v-2z\"\/><\/svg><\/button>\n<\/div>\n<div class=\"rdx-chips\" id=\"rdxChips\" role=\"group\" aria-label=\"Chapters\"><\/div>\n<\/section>\n\n<p class=\"ols-cc-rdx-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\/redox.js?v=20260928c\"><\/script>\n\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\/core-practical-redox-apparatus.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\/core-practical-redox-apparatus.jpg\" alt=\"Manganate(VII) titration: burette of purple KMnO\u2084 read at the top of the meniscus over a flask of acidified Fe\u00b2\u207a, with the pale pink end point\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>A manganate(VII) titration: read the top of the meniscus of the dark purple solution, and stop at the first permanent pale pink colour.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Technique point:<\/strong> The pale green of iron(II) and the pale yellow of iron(III) are so faint at this dilution that the flask looks colourless until the end point.<\/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: Iron in an Iron Tablet<\/h2>\n<p>Order the method for a different sample analysed with the same titration.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1056\" class=\"h5p-iframe\" data-content-id=\"1056\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Redox Titrations Practical Order: Iron in an Iron Tablet\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">4<\/div>\n<h2>The Chemistry: Half-Equations and the 1 : 5 Ratio<\/h2>\n<\/div>\n<p>Manganate(VII) is reduced from +7 to +2 and gains five electrons; each iron(II) ion loses one. Five iron(II) ions are therefore needed for each manganate(VII) ion.<\/p>\n<p class=\"ols-equation\">MnO\u2084\u207b(aq) + 8H\u207a(aq) + 5e\u207b \u2192 Mn\u00b2\u207a(aq) + 4H\u2082O(l)<\/p>\n<p class=\"ols-equation\">Fe\u00b2\u207a(aq) \u2192 Fe\u00b3\u207a(aq) + e\u207b   (\u00d7 5)<\/p>\n<p class=\"ols-equation\">MnO\u2084\u207b(aq) + 5Fe\u00b2\u207a(aq) + 8H\u207a(aq) \u2192 Mn\u00b2\u207a(aq) + 5Fe\u00b3\u207a(aq) + 4H\u2082O(l)<\/p>\n<p>The titration is <strong>self-indicating<\/strong>. MnO\u2084\u207b is intensely purple and Mn\u00b2\u207a is almost colourless at this concentration, so each drop is decolourised while iron(II) remains, and the first drop in excess turns the whole solution pale pink.<\/p>\n<h3>Why sulfuric acid, and not another acid<\/h3>\n<p>The acid supplies the H\u207a in the half-equation. <strong>Hydrochloric acid<\/strong> cannot be used, because manganate(VII) oxidises chloride ions to chlorine; some titrant is used up on the acid, and the titre is too high.<\/p><p><strong>Nitric acid<\/strong> is itself an oxidising agent and could oxidise some iron(II) before the titration, making the titre too low. <strong>Ethanoic acid<\/strong> is a weak acid and does not supply enough H\u207a.<\/p><p>If there is too little acid, manganate(VII) is reduced only to manganese(IV) oxide, a brown precipitate, and the 1 : 5 ratio no longer holds.<\/p><p>Dilute sulfuric acid is neither oxidised nor an oxidising agent under these conditions, so it is the acid to use.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam wording:<\/strong> &#8220;Dilute sulfuric acid is used because it provides H\u207a ions but is not oxidised by manganate(VII); hydrochloric acid would be oxidised to chlorine, using up extra manganate(VII).&#8221;<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>Worked Calculation: Iron(II)<\/h2>\n<\/div>\n<p>The table gives a complete set of results for 25.0 cm\u00b3 portions of an iron(II) solution titrated with 0.0200 mol dm\u207b\u00b3 KMnO\u2084. Readings are to the nearest 0.05 cm\u00b3, taken at the top of the meniscus.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Titration<\/th><th>Rough<\/th><th>1<\/th><th>2<\/th><th>3<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Final reading \/ cm\u00b3<\/strong><\/td><td>25.10<\/td><td>24.70<\/td><td>24.90<\/td><td>24.95<\/td><\/tr>\n<tr><td><strong>Initial reading \/ cm\u00b3<\/strong><\/td><td>0.00<\/td><td>0.10<\/td><td>0.25<\/td><td>0.40<\/td><\/tr>\n<tr><td><strong>Titre \/ cm\u00b3<\/strong><\/td><td>25.10<\/td><td>24.60<\/td><td>24.65<\/td><td>24.55<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Titres 1, 2 and 3 are concordant (all within 0.10 cm\u00b3), so the mean titre is (24.60 + 24.65 + 24.55) \u00f7 3 = 24.60 cm\u00b3; the rough titre is not used.<\/p>\n<p class=\"ols-equation\">Step 1: moles of MnO\u2084\u207b = 0.0200 \u00d7 24.60 \u00f7 1000 = 4.92 \u00d7 10\u207b\u2074 mol<\/p>\n<p class=\"ols-equation\">Step 2: moles of Fe\u00b2\u207a = 5 \u00d7 4.92 \u00d7 10\u207b\u2074 = 2.46 \u00d7 10\u207b\u00b3 mol<\/p>\n<p class=\"ols-equation\">Step 3: [Fe\u00b2\u207a] = 2.46 \u00d7 10\u207b\u00b3 \u00f7 0.0250 = 0.0984 mol dm\u207b\u00b3<\/p>\n<p><strong>Answer:<\/strong> 0.0984 mol dm\u207b\u00b3. If the solution was made by dissolving 9.80 g of ammonium iron(II) sulfate, (NH\u2084)\u2082Fe(SO\u2084)\u2082\u00b76H\u2082O (Mr 392.0), in 250 cm\u00b3, the expected concentration is 9.80 \u00f7 392.0 \u00f7 0.250 = 0.100 mol dm\u207b\u00b3, so the salt is 0.0984 \u00f7 0.100 \u00d7 100 = 98.4% pure. The value is given to three significant figures, the precision of the concentration of KMnO\u2084.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Unit check:<\/strong> cm\u00b3 \u00f7 1000 = dm\u00b3; mol dm\u207b\u00b3 \u00d7 dm\u00b3 = mol; mol \u00f7 dm\u00b3 = mol dm\u207b\u00b3. Multiply by 5 for Fe\u00b2\u207a because one MnO\u2084\u207b reacts with five Fe\u00b2\u207a.<\/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: A Nitrite Titration<\/h2>\n<p>Apply the same method to a different reducing agent with a different ratio.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1057\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">6<\/div>\n<h2>Hydrogen Peroxide and Ethanedioate: the 2 : 5 Ratio<\/h2>\n<\/div>\n<p>Hydrogen peroxide and ethanedioate (oxalate) each lose two electrons, so two manganate(VII) ions (ten electrons) react with five of them.<\/p>\n<p class=\"ols-equation\">H\u2082O\u2082(aq) \u2192 O\u2082(g) + 2H\u207a(aq) + 2e\u207b<\/p>\n<p class=\"ols-equation\">2MnO\u2084\u207b(aq) + 5H\u2082O\u2082(aq) + 6H\u207a(aq) \u2192 2Mn\u00b2\u207a(aq) + 5O\u2082(g) + 8H\u2082O(l)<\/p>\n<p class=\"ols-equation\">C\u2082O\u2084\u00b2\u207b(aq) \u2192 2CO\u2082(g) + 2e\u207b<\/p>\n<p class=\"ols-equation\">2MnO\u2084\u207b(aq) + 5C\u2082O\u2084\u00b2\u207b(aq) + 16H\u207a(aq) \u2192 2Mn\u00b2\u207a(aq) + 10CO\u2082(g) + 8H\u2082O(l)<\/p>\n<p>The ethanedioate titration is carried out <strong>warm<\/strong>, at about 60 \u00b0C, because the reaction is very slow at room temperature: the first drops of manganate(VII) stay purple for several seconds.<\/p>\n<p>The reaction then speeds up as it goes, because the Mn\u00b2\u207a ions it produces <strong>catalyse<\/strong> it. This is <strong>autocatalysis<\/strong>, and it is why the colour of later drops disappears almost at once.<\/p>\n<p>The reaction is slow at first because it needs two negative ions, MnO\u2084\u207b and C\u2082O\u2084\u00b2\u207b, to react, and they repel each other; the Mn\u00b2\u207a catalyst provides a route with a lower activation energy.<\/p>\n<p><strong>Worked Example.<\/strong> Sodium ethanedioate is a primary standard, so it is used to find the exact concentration of a manganate(VII) solution. 25.0 cm\u00b3 of 0.0500 mol dm\u207b\u00b3 Na\u2082C\u2082O\u2084 needs a mean titre of 25.00 cm\u00b3 of KMnO\u2084(aq). Moles of C\u2082O\u2084\u00b2\u207b = 0.0500 \u00d7 25.0 \u00f7 1000 = 1.25 \u00d7 10\u207b\u00b3 mol; moles of MnO\u2084\u207b = 1.25 \u00d7 10\u207b\u00b3 \u00d7 2 \u00f7 5 = 5.00 \u00d7 10\u207b\u2074 mol; <strong>[KMnO\u2084] = 5.00 \u00d7 10\u207b\u2074 \u00f7 0.02500 = 0.0200 mol dm\u207b\u00b3<\/strong>.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Remember:<\/strong> Fe\u00b2\u207a: 1 MnO\u2084\u207b to 5 Fe\u00b2\u207a. H\u2082O\u2082 and C\u2082O\u2084\u00b2\u207b: 2 MnO\u2084\u207b to 5. Write both half-equations and balance the electrons rather than remembering the ratio.<\/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: Choosing the Conditions<\/h2>\n<p>Choose the correct statements about acids, indicators, starch and autocatalysis in new situations.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1058\" class=\"h5p-iframe\" data-content-id=\"1058\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Redox Titrations Practical Summary: Choosing the Conditions\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">7<\/div>\n<h2>Iodine\u2013Thiosulfate Titrations<\/h2>\n<\/div>\n<p>Thiosulfate ions reduce iodine to iodide ions and are themselves oxidised to tetrathionate ions. Two thiosulfate ions react with each iodine molecule.<\/p>\n<p class=\"ols-equation\">I\u2082(aq) + 2S\u2082O\u2083\u00b2\u207b(aq) \u2192 2I\u207b(aq) + S\u2084O\u2086\u00b2\u207b(aq)<\/p>\n<p>The iodine is usually made in the flask by an oxidising agent that is being analysed, reacting with an <strong>excess of potassium iodide<\/strong>. The amount of iodine liberated depends only on the oxidising agent, because the iodide is in excess.<\/p>\n<p class=\"ols-equation\">2Cu\u00b2\u207a(aq) + 4I\u207b(aq) \u2192 2CuI(s) + I\u2082(aq)<\/p>\n<p class=\"ols-equation\">IO\u2083\u207b(aq) + 5I\u207b(aq) + 6H\u207a(aq) \u2192 3I\u2082(aq) + 3H\u2082O(l)<\/p>\n<p>The end point uses <strong>starch<\/strong>. Thiosulfate is added until the brown iodine colour fades to <strong>pale straw<\/strong> (pale yellow).<\/p>\n<p>About 1 cm\u00b3 of starch solution is then added, giving a <strong>blue-black<\/strong> colour, and thiosulfate is added dropwise until the blue-black colour just disappears.<\/p>\n<p>Starch is added near the end point, not at the start, because a large amount of iodine binds to starch and is released only slowly, so the colour change is late and gradual.<\/p>\n<p>With copper(II), the white precipitate of copper(I) iodide stays in the flask, so the mixture at the end point is off-white rather than colourless; the end point is still the disappearance of the blue-black colour.<\/p>\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\/core-practical-redox-endpoints.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\/core-practical-redox-endpoints.jpg\" alt=\"Iodine\u2013thiosulfate end point in four stages: brown, pale straw, blue-black after starch, then colourless\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>The iodine\u2013thiosulfate end point: brown iodine, pale straw, blue-black once starch is added, then colourless; with copper(II), an off-white precipitate of CuI remains.<\/p><\/div>\n<\/div>\n<p><strong>Worked Example.<\/strong> 25.0 cm\u00b3 of copper(II) sulfate solution is added to excess KI, and the iodine liberated needs a mean titre of 22.40 cm\u00b3 of 0.100 mol dm\u207b\u00b3 Na\u2082S\u2082O\u2083.<\/p>\n<p class=\"ols-equation\">Step 1: moles of S\u2082O\u2083\u00b2\u207b = 0.100 \u00d7 22.40 \u00f7 1000 = 2.24 \u00d7 10\u207b\u00b3 mol<\/p>\n<p class=\"ols-equation\">Step 2: moles of I\u2082 = 2.24 \u00d7 10\u207b\u00b3 \u00f7 2 = 1.12 \u00d7 10\u207b\u00b3 mol<\/p>\n<p class=\"ols-equation\">Step 3: moles of Cu\u00b2\u207a = 2 \u00d7 1.12 \u00d7 10\u207b\u00b3 = 2.24 \u00d7 10\u207b\u00b3 mol, so Cu\u00b2\u207a : S\u2082O\u2083\u00b2\u207b = 1 : 1<\/p>\n<p class=\"ols-equation\">Step 4: [Cu\u00b2\u207a] = 2.24 \u00d7 10\u207b\u00b3 \u00f7 0.0250 = 0.0896 mol dm\u207b\u00b3<\/p>\n<p><strong>Answer:<\/strong> 0.0896 mol dm\u207b\u00b3. For iodate(V), one IO\u2083\u207b gives three I\u2082, which need six S\u2082O\u2083\u00b2\u207b, so IO\u2083\u207b : S\u2082O\u2083\u00b2\u207b = 1 : 6.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam wording:<\/strong> &#8220;Add thiosulfate until the solution is pale straw, then add starch: the blue-black colour disappears at the end point. Starch is added near the end point because iodine bound to starch is released slowly.&#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: Bleach by Iodine\u2013Thiosulfate<\/h2>\n<p>Chain two equations for a different oxidising agent.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-1059\" class=\"h5p-iframe\" data-content-id=\"1059\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Redox Titrations Practical Fill In: Bleach by Iodine\u2013Thiosulfate\"><\/iframe><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">8<\/div>\n<h2>Errors, Uncertainty and Improvements<\/h2>\n<\/div>\n<p>The burette and pipette uncertainties are the same as in any titration; the redox chemistry adds its own sources of error.<\/p>\n<div class=\"ols-table-wrap\">\n<table class=\"ols-table\">\n<thead>\n<tr><th>Source of error<\/th><th>Effect on the titre<\/th><th>Improvement<\/th><\/tr>\n<\/thead>\n<tbody>\n<tr><td><strong>Iron(II) solution oxidised by air on standing<\/strong><\/td><td>Less Fe\u00b2\u207a left: titre too low<\/td><td>Make the solution fresh, in dilute sulfuric acid, and titrate promptly<\/td><\/tr>\n<tr><td><strong>Too little acid in the flask<\/strong><\/td><td>Brown MnO\u2082 forms, the ratio changes and the end point is unclear<\/td><td>Add an excess of dilute sulfuric acid; if brown appears, discard the run<\/td><\/tr>\n<tr><td><strong>Hydrochloric acid used instead of sulfuric acid<\/strong><\/td><td>Some MnO\u2084\u207b oxidises Cl\u207b: titre too high<\/td><td>Use dilute sulfuric acid only<\/td><\/tr>\n<tr><td><strong>Ethanedioate titrated cold<\/strong><\/td><td>Slow reaction: the pink persists too early and the end point is overshot<\/td><td>Warm to about 60 \u00b0C and add slowly at first<\/td><\/tr>\n<tr><td><strong>Starch added at the start<\/strong><\/td><td>End point late and gradual: titre too high<\/td><td>Add starch only when the solution is pale straw<\/td><\/tr>\n<tr><td><strong>Iodine lost by evaporation<\/strong><\/td><td>Less iodine to titrate: titre too low<\/td><td>Titrate as soon as the iodine is liberated; keep the flask cool<\/td><\/tr>\n<tr><td><strong>Reading the top of the meniscus once and the bottom once<\/strong><\/td><td>Titre wrong by the height of the meniscus<\/td><td>Read the top of the meniscus for every KMnO\u2084 reading<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><strong>Percentage uncertainties.<\/strong> Each burette reading is \u00b10.05 cm\u00b3, so a titre carries \u00b10.10 cm\u00b3: for 24.60 cm\u00b3, 0.10 \u00f7 24.60 \u00d7 100 = 0.41%. The 25.0 cm\u00b3 pipette (\u00b10.06 cm\u00b3) adds 0.06 \u00f7 25.0 \u00d7 100 = 0.24%. The total, about 0.65%, is small beside the chemical errors above, which is why the evaluation mark usually goes to one of those.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> For every error, say which way the titre moves and why: &#8220;the titre is too high because some manganate(VII) is used up oxidising chloride ions&#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: Errors in Redox Titrations<\/h2>\n<p>Evaluate new situations in redox titrations.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1060\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">9<\/div>\n<h2>Common Mistakes<\/h2>\n<\/div>\n<p>The same errors appear in students&#8217; write-ups and exam answers year after year. Each one costs a mark that the corrected version earns.<\/p>\n<ul>\n<li>Using a 1 : 1 ratio for manganate(VII) and iron(II). The ratio is <strong>1 : 5<\/strong>; for H\u2082O\u2082 and ethanedioate it is 2 : 5.<\/li>\n<li>Describing the manganate(VII) end point as &#8220;purple to colourless&#8221;. The flask goes from colourless to the <strong>first permanent pale pink<\/strong>.<\/li>\n<li>Adding an indicator to a manganate(VII) titration.<\/li>\n<li>Choosing hydrochloric acid to acidify, or saying only that sulfuric acid &#8220;provides H\u207a&#8221; without saying why HCl cannot be used.<\/li>\n<li>Adding starch at the start of an iodine\u2013thiosulfate titration.<\/li>\n<li>Forgetting the factor of 2 between iodine and thiosulfate, or between Cu\u00b2\u207a and I\u2082.<\/li>\n<li>Reading the bottom of the meniscus of manganate(VII), which cannot be seen clearly.<\/li>\n<\/ul>\n<\/article>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">10<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Say<\/h3><p>&#8220;Manganate(VII) is self-indicating: the end point is the first permanent pale pink.&#8221; &#8220;Sulfuric acid is used because hydrochloric acid would be oxidised to chlorine by manganate(VII).&#8221; &#8220;Starch is added near the end point, when the solution is pale straw; the blue-black colour disappears at the end point.&#8221;<\/p>\n<h3>Do not say<\/h3><p>&#8220;The indicator is potassium manganate(VII).&#8221; (It is the titrant; no indicator is added.) &#8220;The end point is when the solution turns purple.&#8221; &#8220;MnO\u2084\u207b reacts with Fe\u00b2\u207a in a 1 : 1 ratio.&#8221;<\/p>\n<h3>Watch for<\/h3><p>Half-equations you must combine to get the ratio; percentage purity of a salt or the mass of iron in a tablet; the autocatalysis curve of the ethanedioate titration; two-stage iodine calculations (oxidising agent \u2192 I\u2082 \u2192 S\u2082O\u2083\u00b2\u207b); readings recorded to 0.05 cm\u00b3 and concordance within 0.10 cm\u00b3 of each other.<\/p>\n<\/article>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Short answers to the questions students most often ask about redox titrations.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>Why is no indicator needed with potassium manganate(VII)?<\/h3>\n<p>Because manganate(VII) is intensely purple and its product, Mn\u00b2\u207a, is almost colourless. While there is still reducing agent in the flask each drop is decolourised; the first drop in excess turns the solution pale pink, which is the end point.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why do we read the top of the meniscus?<\/h3>\n<p>Manganate(VII) solution is so dark that the bottom of the meniscus cannot be seen. Reading the top every time gives the correct titre, because both readings are offset by the same amount.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why is the ethanedioate titration done warm, and why does it speed up?<\/h3>\n<p>The reaction between two negative ions is very slow at room temperature, so it is warmed to about 60 \u00b0C. It then speeds up because the Mn\u00b2\u207a ions it makes catalyse the reaction, which is called autocatalysis.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>When exactly should I add the starch?<\/h3>\n<p>When the brown iodine has faded to a pale straw colour. Added earlier, much of the iodine binds to the starch and is released only slowly, so the blue-black colour fades gradually and the end point is late.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>How do I get the mole ratio if I cannot remember it?<\/h3>\n<p>Write the two half-equations, multiply them so that the electrons lost equal the electrons gained, and add them. The coefficients of the two reactants give the ratio: 1 : 5 for MnO\u2084\u207b and Fe\u00b2\u207a, 2 : 5 for MnO\u2084\u207b and H\u2082O\u2082 or C\u2082O\u2084\u00b2\u207b, 1 : 2 for I\u2082 and S\u2082O\u2083\u00b2\u207b.<\/p>\n<\/div>\n<\/div>\n<\/section>\n<section class=\"ols-related-card\">\n<h2>Related Practical Skills Pages<\/h2>\n<p>Use these pages to connect the practical techniques with each other and with 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\/practical-skills\/molar-volume-of-a-gas\/\">Gas collection: Molar Volume of a Gas<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/enthalpy-change-via-hess-law\/\">Thermometry: Enthalpy Change via Hess&#8217;s Law<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/concentration-of-hcl-by-titration\/\">Titration: Concentration of HCl by Titration<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/preparation-of-a-standard-solution\/\">Standard solution: Preparation of a Standard Solution<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/rates-of-hydrolysis-of-halogenoalkanes\/\">Hydrolysis rates: Hydrolysis of Halogenoalkanes<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/preparing-an-organic-liquid-chlorination-of-2-methylpropan-2-ol\/\">Organic prep: Chlorination of 2-methylpropan-2-ol<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/oxidation-of-an-alcohol-distillation-and-reflux\/\">Distil or reflux: Oxidation of an Alcohol<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/qualitative-analysis-of-inorganic-and-organic-unknowns\/\">Qualitative analysis: Analysis of Inorganic and Organic Unknowns<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/rates-of-reaction-timing-an-observation\/\">Rates: Rates of Reaction<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/gravimetric-analysis-water-of-crystallisation\/\">Gravimetric: Gravimetric and Composition Analysis<\/a>\n<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/practical-skills\/\">Practical Skills (Paper 3) 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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