{"id":12386,"date":"2026-09-30T19:40:46","date_gmt":"2026-09-30T18:40:46","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/"},"modified":"2026-10-03T11:51:50","modified_gmt":"2026-10-03T10:51:50","slug":"activation-energy-and-the-arrhenius-equation","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/","title":{"rendered":"Activation Energy and the Arrhenius Equation"},"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      --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; 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: none; }\n      .ols-table td::before { content: attr(data-label); display: block; margin-bottom: 6px; font-size: 13px; font-weight: 700; color: var(--blue); }\n      .ols-author { align-items: flex-start; padding: 22px 18px; border-radius: 22px; }\n      .ols-author-avatar-img { width: 72px; height: 72px; }\n      .ols-author-title { font-size: 24px; }\n      .ols-author-description { font-size: 15px; }\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<\/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() {\r\n    var sidebar = document.querySelector('.ols-sidebar');\r\n    if (!sidebar) return false;\r\n\r\n    var currentPath = normalisePath(window.location.pathname);\r\n    var links = sidebar.querySelectorAll('a[href]');\r\n    var matched = null;\r\n    var matchedLength = 0;\r\n\r\n    sidebar.querySelectorAll('.active, .active-main, .parent-active').forEach(function(item) {\r\n      item.classList.remove('active', 'active-main', 'parent-active');\r\n    });\r\n\r\n    sidebar.querySelectorAll('a[data-ols-disabled-parent=\"1\"], a[aria-current]').forEach(function(a) {\r\n      a.removeAttribute('aria-current');\r\n      a.removeAttribute('tabindex');\r\n      a.removeAttribute('data-ols-disabled-parent');\r\n    });\r\n\r\n    links.forEach(function(a) {\r\n      try {\r\n        var href = a.getAttribute('href');\r\n        if (!href || href === '#' || href.charAt(0) === '#') return;\r\n        var linkPath = normalisePath(new URL(href, window.location.origin).pathname);\r\n        if (!linkPath) return;\r\n        if (currentPath === linkPath || currentPath.indexOf(linkPath + '\/') === 0) {\r\n          if (linkPath.length > matchedLength) {\r\n            matched = a;\r\n            matchedLength = linkPath.length;\r\n          }\r\n        }\r\n      } catch(e) {}\r\n    });\r\n\r\n    if (matched) {\r\n      var matchedLi = matched.closest('li');\r\n      var parentSub = matched.closest('.ols-subtopic-list');\r\n\r\n      if (parentSub) {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('active');\r\n          matched.setAttribute('aria-current', 'page');\r\n        }\r\n\r\n        var parentLi = parentSub.closest('li');\r\n        while (parentLi) {\r\n          parentLi.classList.add('parent-active', 'active-main');\r\n\r\n          var parentLink = parentLi.querySelector(':scope > a');\r\n          if (parentLink) {\r\n            parentLink.setAttribute('aria-current', 'true');\r\n            parentLink.setAttribute('tabindex', '-1');\r\n            parentLink.setAttribute('data-ols-disabled-parent', '1');\r\n          }\r\n\r\n          var higherSub = parentLi.parentElement.closest('.ols-subtopic-list');\r\n          parentLi = higherSub ? higherSub.closest('li') : null;\r\n        }\r\n      } else {\r\n        if (matchedLi) {\r\n          matchedLi.classList.add('parent-active', 'active-main');\r\n          matched.setAttribute('aria-current', 'page');\r\n          matched.setAttribute('tabindex', '-1');\r\n          matched.setAttribute('data-ols-disabled-parent', '1');\r\n        }\r\n      }\r\n    }\r\n\r\n    return true;\r\n  }\r\n\r\n  if (!highlightActive()) {\r\n    document.addEventListener('DOMContentLoaded', highlightActive);\r\n  }\r\n})();\r\n<\/script>\n\n  <main class=\"ols-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n<a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/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>Activation Energy and the Arrhenius Equation<\/span>\n<\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>Activation Energy and the Arrhenius Equation<\/h1>\n        <p class=\"ols-page-intro\">A concise revision guide to how temperature changes the rate constant: the Arrhenius equation k = Ae^(\u2212E\u2090\/RT), the straight-line form ln k = \u2212E\u2090\/RT + ln A, finding the activation energy from the gradient of a graph of ln k against 1\/T.<\/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>Temperature and the Rate Constant<\/h2>\n<\/div>\n<p>Concentration changes affect the rate through the rate equation, but they leave k alone. Temperature is different: the <strong>rate constant itself increases with temperature<\/strong>, and for many reactions a rise of about 10 \u00b0C roughly doubles it.<\/p><p>Collision theory explains why. Warmer particles collide only slightly more often, but the <strong>fraction of collisions with energy of at least the activation energy<\/strong>, E\u2090, rises steeply.<\/p><p>This is because the high-energy tail of the Boltzmann distribution grows much faster than the average. The rate constant is the measure of how likely a collision is to succeed, so it grows with that fraction.<\/p>\n<p>The same idea explains a catalyst in terms of k: by providing a route with a lower E\u2090, the catalyst increases the fraction of collisions that can react at a given temperature, so k for the catalysed reaction is larger.<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Key idea:<\/strong> Concentration changes the rate; temperature (and a catalyst) changes the rate constant. A higher temperature means a larger k because a larger fraction of collisions have E \u2265 E\u2090.<\/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: Temperature and k<\/h2>\n<p>Qualitative questions on why k rises with temperature and what happens to k, and to the rate, when conditions change in reactions not mentioned on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1093\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">2<\/div>\n<h2>The Arrhenius Equation<\/h2>\n<\/div>\n<p>The relationship between k and temperature is the <strong>Arrhenius equation<\/strong>:<\/p>\n<p style=\"text-align:center\"><strong>k = Ae^(\u2212E\u2090\/RT)<\/strong><\/p>\n<div class=\"ols-table-wrap\"><table class=\"ols-table\"><thead><tr><th>Symbol<\/th><th>Meaning<\/th><\/tr><\/thead><tbody><tr><td><strong>A<\/strong><\/td><td>The <strong>pre-exponential factor<\/strong> (also called the Arrhenius constant or frequency factor), a constant for the reaction that has the <strong>same units as k<\/strong><\/td><\/tr><tr><td><strong>E\u2090<\/strong><\/td><td>The activation energy in J mol\u207b\u00b9<\/td><\/tr><tr><td><strong>R<\/strong><\/td><td>The gas constant, 8.31 J K\u207b\u00b9 mol\u207b\u00b9<\/td><\/tr><tr><td><strong>T<\/strong><\/td><td>The temperature in <strong>kelvin<\/strong><\/td><\/tr><\/tbody><\/table><\/div><p>Here the exponential term, e^(\u2212E\u2090\/RT), is the <strong>fraction of collisions with energy of at least E\u2090<\/strong>; it is always between 0 and 1 and it rises towards 1 as T rises.<\/p><p>A represents the rate constant the reaction would have if every collision were successful. It includes the collision frequency and the fraction of collisions with the right orientation.<\/p>\n<p>The equation shows the two things that make a reaction fast: a large A (frequent, well-oriented collisions) and a small E\u2090.<\/p><p>It also shows why the effect of temperature is so large: because E\u2090\/RT sits in an exponent, a small change in T makes a big change in e^(\u2212E\u2090\/RT).<\/p><div class=\"ols-key-box\"><p><strong>Remember:<\/strong> the equation is given on the data sheet if it is needed; what has to be known is what each symbol means and how to use it.<\/p><\/div>\n<div class=\"ols-key-box\">\n<p><strong>Definition:<\/strong> k = Ae^(\u2212E\u2090\/RT): A, the pre-exponential factor with the units of k; E\u2090, the activation energy in J mol\u207b\u00b9; R = 8.31 J K\u207b\u00b9 mol\u207b\u00b9; T in K.<\/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-arrsymbols.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-arrsymbols.jpg\" alt=\"Labelled Arrhenius equation with the meaning and unit of each symbol and a table of the energy fraction at three temperatures.\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>Each symbol in k = Ae^(\u2212E\u2090\/RT) has a fixed meaning and unit, and the exponential term is the fraction of collisions with enough energy, which roughly doubles for a 10 K rise.<\/p><\/div>\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>The Straight-Line Form<\/h2>\n<\/div>\n<p>Taking natural logarithms of both sides turns the exponential into something that can be plotted as a straight line:<\/p>\n<p style=\"text-align:center\"><strong>ln k = \u2212E\u2090\/R \u00d7 1\/T + ln A<\/strong><\/p>\n<p>Compare this with y = mx + c. If <strong>ln k is plotted on the y-axis against 1\/T on the x-axis<\/strong>, the points lie on a straight line with <strong>gradient \u2212E\u2090\/R<\/strong> and <strong>intercept ln A<\/strong>.<\/p><p>The gradient is negative because k falls as 1\/T rises (that is, as T falls).<\/p><p>Multiplying the gradient by \u2212R gives E\u2090; taking the exponential of the intercept gives A.<\/p>\n<p>In a real experiment k is rarely measured directly. Instead a reaction is timed at several temperatures with the same starting concentrations.<\/p><p>At fixed concentrations the rate is proportional to k, and in a clock reaction the rate is proportional to 1\/t, so <strong>ln(rate) or ln(1\/t) can be plotted instead of ln k<\/strong>.<\/p><p>The intercept changes, because the constant of proportionality is absorbed into it, but the gradient, and therefore E\u2090, is the same.<\/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\/kinetics-t11-07-arrhenius-graph.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-t11-07-arrhenius-graph.jpg\" alt=\"Arrhenius plot of ln k against 1\/T with a gradient of \u22128300 K, giving an activation energy of 69 kJ mol\u207b\u00b9\">\n<\/a>\n<\/div>\n<div class=\"ols-zoom-card-caption\"><p>The Arrhenius plot: ln k against 1\/T is a straight line of gradient \u2212E\u2090\/R, with the data and the working for E\u2090.<\/p><\/div>\n<\/div>\n<div class=\"ols-key-box\">\n<p><strong>Exam wording:<\/strong> &#8220;A graph of ln k against 1\/T is a straight line with gradient \u2212E\u2090\/R and intercept ln A, so E\u2090 = \u2212gradient \u00d7 R.&#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: The Arrhenius Graph<\/h2>\n<p>What is plotted on each axis, what the gradient and the intercept give, and why ln(1\/t) can stand in for ln k, for data sets not shown on this page.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1094\"><\/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>Finding E\u2090 From a Graph<\/h2>\n<\/div>\n<p>The figure above gives k at four temperatures. The steps are always the same:<\/p>\n<ol><li>Convert each temperature to kelvin and calculate <strong>1\/T<\/strong> (typically 2.5 \u00d7 10\u207b\u00b3 to 3.5 \u00d7 10\u207b\u00b3 K\u207b\u00b9).<\/li><li>Calculate <strong>ln k<\/strong> (or ln(1\/t)) for each run; the values are negative for small k.<\/li><li>Plot ln k against 1\/T and draw the <strong>best-fit straight line<\/strong>.<\/li><li>Measure the gradient using a <strong>large triangle<\/strong> with points far apart on the line, not two of the data points.<\/li><li>E\u2090 = \u2212gradient \u00d7 R, in J mol\u207b\u00b9; divide by 1000 for kJ mol\u207b\u00b9.<\/li><\/ol>\n<p><strong>Step 1:<\/strong> From the plotted data the gradient is \u22128300 K (the unit of the gradient is K, because ln k has no unit and 1\/T is in K\u207b\u00b9).<\/p><p><strong>Step 2:<\/strong> So E\u2090 = 8300 \u00d7 8.31 = 69 000 J mol\u207b\u00b9.<\/p><p><strong>Answer:<\/strong> E\u2090 = <strong>69 kJ mol\u207b\u00b9<\/strong>, which is a typical value for a reaction that is conveniently slow at room temperature.<\/p><p>If the intercept is required, extending the line to 1\/T = 0 gives ln A, and A = e^(ln A).<\/p>\n<div class=\"ols-key-box\">\n<p><strong>Exam focus:<\/strong> Three marks usually hide here: the gradient with its sign, multiplying by R (not dividing), and converting J to kJ. Quote E\u2090 as a positive number with its unit.<\/p>\n<\/div>\n<\/article>\n<article class=\"ols-note-card soft\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">5<\/div>\n<h2>What the Specification Asks<\/h2>\n<\/div>\n<p>Your specification asks for the <strong>qualitative<\/strong> effect of temperature on the rate constant: k increases with temperature because a greater fraction of collisions have energy of at least E\u2090.<\/p>\n<p>The Arrhenius equation and the graph above are shown so that you can see where that statement comes from and can read an ln k against 1\/T plot if one is given.<\/p>\n<div class=\"ols-key-box\"><p><strong>Exam focus:<\/strong> You will not be asked to calculate A or E\u2090 from the equation. Paper 5 planning questions may still ask you to plan a rate experiment at several temperatures and to say how the results would be processed.<\/p><\/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: Gradient, Intercept and Units<\/h2>\n<p>Read a gradient and an intercept from Arrhenius data not used above, get the sign of E\u2090 right and give it in the correct unit.<\/p>\n<div class=\"ols-h5p-frame\"><div class=\"h5p-content\" data-content-id=\"1095\"><\/div><\/div>\n<\/section>\n<article class=\"ols-note-card\">\n<div class=\"ols-note-title\">\n<div class=\"ols-note-icon\">6<\/div>\n<h2>Common Exam Points<\/h2>\n<\/div>\n<h3>Say<\/h3><p>&#8220;The rate constant increases with temperature because a greater proportion of collisions have energy \u2265 E\u2090.&#8221; &#8220;Plot ln k against 1\/T; gradient = \u2212E\u2090\/R; E\u2090 = \u2212gradient \u00d7 R.&#8221; &#8220;T must be in kelvin.&#8221;<\/p>\n<h3>Do not say<\/h3><p>&#8220;The activation energy decreases when the temperature rises&#8221; (E\u2090 is fixed; the fraction of collisions that reach it rises). &#8220;Concentration changes k.&#8221; &#8220;E\u2090 = gradient&#8221; without the \u2212R.<\/p>\n<h3>Watch for<\/h3><p>Data given in \u00b0C, rates given as times, and E\u2090 asked for in kJ mol\u207b\u00b9 when R is in J: convert every time. The gradient of an ln k against 1\/T graph is always negative; a positive E\u2090 follows from the minus sign in \u2212E\u2090\/R.<\/p>\n<\/article>\n<section class=\"ols-faq-card\">\n<h2>FAQs<\/h2>\n<p>Use these quick answers to check the Arrhenius ideas.<\/p>\n\n<div class=\"ols-faq-list\">\n<div class=\"ols-faq-item\">\n<h3>Why do we plot ln k against 1\/T and not k against T?<\/h3>\n<p>Because k against T is a curve, from which you cannot read E\u2090. Taking natural logarithms gives ln k = \u2212E\u2090\/RT + ln A, which has the form y = mx + c with x = 1\/T, so the graph is a straight line whose gradient is \u2212E\u2090\/R.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Why is the gradient negative?<\/h3>\n<p>Because k increases with temperature, and 1\/T decreases as T increases, so ln k falls as 1\/T rises. E\u2090 is positive, so the gradient \u2212E\u2090\/R must be negative; if yours comes out positive you have plotted the axes the wrong way round.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Which units do I use?<\/h3>\n<p>T in kelvin, so 1\/T in K\u207b\u00b9, and R = 8.31 J K\u207b\u00b9 mol\u207b\u00b9. The gradient is then in K, and E\u2090 = \u2212gradient \u00d7 R comes out in J mol\u207b\u00b9; divide by 1000 to quote it in kJ mol\u207b\u00b9. A gradient of about \u22126000 K, for example, gives an E\u2090 of about 50 kJ mol\u207b\u00b9.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>Do I need to do calculations with the Arrhenius equation?<\/h3>\n<p>No. You need the qualitative picture: k rises with temperature and falls with a larger activation energy, because a bigger fraction of collisions has energy above E\u2090, and a catalyst raises k by lowering E\u2090. You will not be asked to calculate E\u2090 from data.<\/p>\n<\/div>\n\n<div class=\"ols-faq-item\">\n<h3>What does the constant A mean?<\/h3>\n<p>The pre-exponential factor. It is related to the collision frequency and the fraction of collisions in the right orientation, and e^(\u2212E\u2090\/RT) is the fraction of collisions with energy above E\u2090. Multiplying the two gives the rate constant.<\/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\/heterogeneous-and-homogeneous-catalysis\/\">Heterogeneous and Homogeneous Catalysis<\/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<a class=\"ols-related-item\" href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-8-reaction-kinetics\/\">Topic 8 Reaction Kinetics (AS)<\/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          var closeButton = lightbox.querySelector(\".ols-image-lightbox-close\");\n          var clickableImages = page.querySelectorAll(\"img.ols-lightbox-target\");\n          function openLightbox(image) {\n            lightboxImage.src = image.currentSrc || image.src;\n            lightboxImage.alt = image.alt || \"Expanded revision image\";\n            lightbox.classList.add(\"is-open\");\n            lightbox.setAttribute(\"aria-hidden\", \"false\");\n            if (!document.body.dataset.olsPreviousOverflow) {\n              document.body.dataset.olsPreviousOverflow = document.body.style.overflow || \"default\";\n            }\n            document.body.style.overflow = \"hidden\";\n          }\n          function closeLightbox() {\n            lightbox.classList.remove(\"is-open\");\n            lightbox.setAttribute(\"aria-hidden\", \"true\");\n            lightboxImage.src = \"\";\n            if (document.body.dataset.olsPreviousOverflow) {\n              document.body.style.overflow = document.body.dataset.olsPreviousOverflow === \"default\" ? \"\" : document.body.dataset.olsPreviousOverflow;\n              delete document.body.dataset.olsPreviousOverflow;\n            }\n          }\n          clickableImages.forEach(function(image){\n            image.addEventListener(\"click\", function(event){\n              event.preventDefault();\n              event.stopPropagation();\n              openLightbox(image);\n            });\n          });\n          closeButton.addEventListener(\"click\", closeLightbox);\n          lightbox.addEventListener(\"click\", function(event){ if (event.target === lightbox) { closeLightbox(); } });\n          document.addEventListener(\"keydown\", function(event){ if (event.key === \"Escape\" && lightbox.classList.contains(\"is-open\")) { closeLightbox(); } });\n        })();\n      <\/script>\n\n      <script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@graph\": [\n    {\n      \"@type\": \"WebPage\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/#webpage\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/\",\n      \"name\": \"Activation Energy and the Arrhenius Equation | Topic 26 Reaction Kinetics | Online Learning System\",\n      \"description\": \"Cambridge International A Level Chemistry revision notes on the Arrhenius equation: temperature and the rate constant, ln k against 1\/T graphs and finding the activation energy from the gradient.\",\n      \"isPartOf\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#website\"\n      },\n      \"breadcrumb\": {\n        \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/#breadcrumb\"\n      }\n    },\n    {\n      \"@type\": \"WebSite\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/#website\",\n      \"url\": \"https:\/\/www.onlinelearningsystem.net\/\",\n      \"name\": \"Online Learning System\"\n    },\n    {\n      \"@type\": \"BreadcrumbList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/#breadcrumb\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\",\n            \"name\": \"Revision Notes\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\",\n            \"name\": \"A Level Chemistry\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/\",\n            \"name\": \"Cambridge International (CIE)\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/\",\n            \"name\": \"Topic 26 Reaction Kinetics\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 5,\n          \"item\": {\n            \"@type\": \"WebPage\",\n            \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/\",\n            \"name\": \"Activation Energy and the Arrhenius Equation\"\n          }\n        }\n      ]\n    },\n    {\n      \"@type\": \"Course\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/#course\",\n      \"name\": \"Activation Energy and the Arrhenius Equation\",\n      \"description\": \"Cambridge International A Level Chemistry revision notes on the Arrhenius equation: temperature and the rate constant, ln k against 1\/T graphs and finding the activation energy from the gradient.\",\n      \"provider\": {\n        \"@type\": \"Organization\",\n        \"name\": \"Online Learning System\",\n        \"url\": \"https:\/\/www.onlinelearningsystem.net\/\"\n      },\n      \"educationalLevel\": \"A Level\",\n      \"about\": [\n        \"Kinetics\",\n        \"Rate equations\",\n        \"Order of reaction\",\n        \"Rate constant\",\n        \"Half-life\",\n        \"Rate-determining step\",\n        \"Arrhenius equation\",\n        \"Catalysis\",\n        \"Physical chemistry\"\n      ],\n      \"hasCourseInstance\": {\n        \"@type\": \"CourseInstance\",\n        \"courseMode\": \"Online\"\n      }\n    },\n    {\n      \"@type\": \"ItemList\",\n      \"@id\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/activation-energy-and-the-arrhenius-equation\/#relatedtopics\",\n      \"name\": \"Related Topic 26 Reaction Kinetics Pages\",\n      \"itemListElement\": [\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 1,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Rate Equations, Orders and the Rate Constant\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-equations-orders-and-the-rate-constant\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on rate equations: orders of reaction, the rate constant k, overall order and working out the units of k.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 2,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Techniques for Measuring Rates\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/techniques-for-measuring-rates\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on measuring rates: titration, colorimetry, mass and gas-volume methods, continuous monitoring and the initial-rates method with clock reactions.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 3,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Concentration\u2013Time Graphs and Half-Life\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/concentration-time-graphs-and-half-life\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on concentration\u2013time graphs: deducing order from the shape, tangents and rates, half-life and first-order reactions, k from the half-life.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 4,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Rate\u2013Concentration Graphs and the Initial-Rates Method\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-concentration-graphs-and-the-initial-rates-method\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on the initial-rates method: rate\u2013concentration graphs, deducing orders from tables of data, writing the rate equation and calculating k.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 5,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"The Iodine\u2013Propanone Reaction\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/the-iodine-propanone-reaction\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on the iodine\u2013propanone reaction: collecting rate data, the orders with respect to iodine, propanone and H\u207a, and deducing the mechanism.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 6,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Rate-Determining Step and Reaction Mechanisms\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/rate-determining-step-and-reaction-mechanisms\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on the rate-determining step: rate equations from mechanisms, mechanisms from rate equations, intermediates, and S\u20991\/S\u20992 evidence from halogenoalkanes hydrolysis.\"\n          }\n        },\n        {\n          \"@type\": \"ListItem\",\n          \"position\": 7,\n          \"item\": {\n            \"@type\": \"Course\",\n            \"name\": \"Heterogeneous and Homogeneous Catalysis\",\n            \"url\": \"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/cie\/topic-26-reaction-kinetics\/heterogeneous-and-homogeneous-catalysis\/\",\n            \"description\": \"Cambridge International A Level Chemistry revision notes on catalysis: heterogeneous catalysts at surfaces (adsorption, desorption, the Haber process, catalytic converters) and homogeneous catalysts that are regenerated.\"\n          }\n        }\n      ]\n    }\n  ]\n}\n<\/script>\n    <\/main>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>Revision Notes \/ A Level Chemistry \/ Cambridge International (CIE) \/ Topic 26 Reaction Kinetics \/ Activation Energy and the Arrhenius Equation Activation Energy and the Arrhenius Equation A concise revision guide to how temperature changes the rate constant: the Arrhenius equation k = Ae^(\u2212E\u2090\/RT), the straight-line form ln k = \u2212E\u2090\/RT + ln A, [&hellip;]<\/p>\n","protected":false},"author":12,"featured_media":0,"parent":12379,"menu_order":6,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-12386","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/12386","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=12386"}],"version-history":[{"count":1,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/12386\/revisions"}],"predecessor-version":[{"id":12890,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/12386\/revisions\/12890"}],"up":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/pages\/12379"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=12386"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}