{"id":4505,"date":"2026-05-28T05:25:04","date_gmt":"2026-05-28T04:25:04","guid":{"rendered":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/cp-2-prepare-a-standard-solution\/"},"modified":"2026-06-10T08:21:05","modified_gmt":"2026-06-10T07:21:05","slug":"cp-2-prepare-a-standard-solution","status":"publish","type":"page","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-2-prepare-a-standard-solution\/","title":{"rendered":"CP 2 &#8211; Prepare a Standard Solution"},"content":{"rendered":"\n<section class=\"ols-cp-page ols-cp2-standard-solution-page\" id=\"ols-cp2-page\">\n  <style>\n    .ols-cp-page {\n      --navy: #1C244B;\n      --blue: #2563eb;\n      --blue-2: #0f4fa8;\n      --soft-blue: #eef4ff;\n      --soft-green: #f0f7f1;\n      --soft-red: #fff7f7;\n      --soft-purple: #f7f0ff;\n      --soft-gold: #fff8e8;\n      --green: #3f8f46;\n      --red: #d94b2b;\n      --gold: #c9973a;\n      --grey-text: #667085;\n      --body-text: #1f2937;\n      --border: rgba(28, 36, 75, 0.14);\n      --shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      --inner-shadow: 0 10px 26px rgba(28, 36, 75, 0.08);\n      font-family: Poppins, Arial, sans-serif;\n      color: var(--navy);\n      background: #ffffff;\n    }\n\n    .ols-cp-page * {\n      box-sizing: border-box;\n    }\n\n    .ols-cp-sidebar-shortcode {\n      max-width: 1180px;\n      margin: 0 auto;\n      padding: 24px 20px 0;\n    }\n\n    .ols-cp-shell {\n      display: block;\n      max-width: 1180px;\n      margin: 0 auto;\n      padding: 24px 20px 60px;\n    }\n\n    .ols-cp-main {\n      min-width: 0;\n      max-width: none;\n    }\n\n    .ols-breadcrumbs {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 8px;\n      margin: 10px 0 22px;\n      font-size: 15px;\n      color: var(--grey-text);\n    }\n\n    .ols-breadcrumbs a,\n    .ols-breadcrumbs span {\n      color: var(--grey-text);\n      text-decoration: none;\n      font-weight: 600;\n    }\n\n    .ols-breadcrumbs a:hover {\n      color: var(--blue);\n      text-decoration: underline;\n      text-underline-offset: 3px;\n    }\n\n    .ols-title-card,\n    .ols-note-card,\n    .ols-related-card,\n    .ols-faq-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 28px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin-bottom: 24px;\n      overflow: visible;\n    }\n\n    .ols-title-card {\n      background: radial-gradient(circle at top right, rgba(37, 99, 235, 0.13), transparent 34%), linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n    }\n\n    .ols-title-card h1 {\n      margin: 0 0 18px;\n      font-size: clamp(34px, 5vw, 58px);\n      line-height: 1.06;\n      font-weight: 850;\n      letter-spacing: -0.04em;\n      color: #111827;\n    }\n\n    .ols-page-intro {\n      font-size: 19px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n      margin: 0 0 22px;\n    }\n\n    .ols-badges {\n      display: flex;\n      flex-wrap: wrap;\n      gap: 12px;\n      margin-bottom: 22px;\n    }\n\n    .ols-badge {\n      display: inline-flex;\n      align-items: center;\n      padding: 9px 14px;\n      border-radius: 999px;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      font-size: 15px;\n      font-weight: 650;\n      color: var(--navy);\n    }\n\n    .ols-author {\n      display: flex;\n      align-items: center;\n      gap: 20px;\n      padding: 28px;\n      border-radius: 28px;\n      background: linear-gradient(135deg, #ffffff 0%, #f8fbff 100%);\n      border: 1px solid rgba(28, 36, 75, 0.12);\n      box-shadow: 0 18px 45px rgba(28, 36, 75, 0.10);\n      margin-top: 22px;\n    }\n\n    .ols-author-avatar-img {\n      width: 92px;\n      height: 92px;\n      border-radius: 50%;\n      object-fit: cover;\n      object-position: center;\n      flex-shrink: 0;\n      border: 4px solid #ffffff;\n      box-shadow:\n        0 14px 32px rgba(28, 36, 75, 0.18),\n        0 0 0 1px rgba(28, 36, 75, 0.10);\n      transition:\n        transform 0.25s ease,\n        box-shadow 0.25s ease;\n    }\n\n    .ols-author:hover .ols-author-avatar-img {\n      transform: scale(1.04);\n      box-shadow:\n        0 20px 42px rgba(28, 36, 75, 0.22),\n        0 0 0 1px rgba(28, 36, 75, 0.10);\n    }\n\n    .ols-author-content {\n      min-width: 0;\n    }\n\n    .ols-author-title {\n      margin: 0 0 4px;\n      font-size: clamp(24px, 3vw, 34px);\n      line-height: 1.15;\n      font-weight: 700;\n      color: var(--navy);\n      letter-spacing: -0.03em;\n    }\n\n    .ols-author-description {\n      margin: 0;\n      font-size: 17px;\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--grey-text);\n    }\n\n    .ols-linkedin-pill {\n      display: inline-flex;\n      align-items: center;\n      justify-content: center;\n      gap: 10px;\n      margin-top: 16px;\n      padding: 11px 18px;\n      border-radius: 999px;\n      background: linear-gradient(135deg, #0A66C2, #004182);\n      color: #ffffff;\n      text-decoration: none;\n      font-size: 14px;\n      line-height: 1;\n      font-weight: 700;\n      letter-spacing: 0.01em;\n      box-shadow: 0 10px 22px rgba(10, 102, 194, 0.24);\n      position: relative;\n      overflow: hidden;\n      transition:\n        transform 0.22s ease,\n        box-shadow 0.22s ease;\n    }\n\n    .ols-linkedin-pill::before {\n      content: \"\";\n      position: absolute;\n      top: 0;\n      left: -120%;\n      width: 100%;\n      height: 100%;\n      background: linear-gradient(\n        120deg,\n        rgba(255,255,255,0) 0%,\n        rgba(255,255,255,0.28) 50%,\n        rgba(255,255,255,0) 100%\n      );\n      transition: left 0.7s ease;\n    }\n\n    .ols-linkedin-pill:hover {\n      transform: translateY(-3px) scale(1.03);\n      box-shadow:\n        0 16px 34px rgba(10, 102, 194, 0.34),\n        0 0 0 6px rgba(10, 102, 194, 0.10);\n      color: #ffffff;\n    }\n\n    .ols-linkedin-pill:hover::before {\n      left: 120%;\n    }\n\n    .ols-linkedin-icon {\n      width: 18px;\n      height: 18px;\n      display: block;\n      flex-shrink: 0;\n    }\n\n    .ols-note-card.soft {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-red) 100%);\n    }\n\n    .ols-note-card.green {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-green) 100%);\n    }\n\n    .ols-note-card.purple {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-purple) 100%);\n    }\n\n    .ols-note-card.gold {\n      background: linear-gradient(135deg, #ffffff 0%, var(--soft-gold) 100%);\n    }\n\n    .ols-note-title {\n      display: flex;\n      align-items: center;\n      gap: 14px;\n      margin-bottom: 20px;\n    }\n\n    .ols-note-icon {\n      width: 52px;\n      height: 52px;\n      border-radius: 16px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-size: 24px;\n      font-weight: 800;\n      flex-shrink: 0;\n    }\n\n    .ols-note-title h2,\n    .ols-related-card h2,\n    .ols-faq-card h2 {\n      margin: 0;\n      font-size: clamp(27px, 3.4vw, 42px);\n      line-height: 1.15;\n      font-weight: 850;\n      color: #111827;\n      letter-spacing: -0.03em;\n    }\n\n    .ols-note-card p,\n    .ols-note-card li,\n    .ols-related-card p,\n    .ols-faq-card p,\n    .ols-faq-card li {\n      font-size: clamp(15px, 1.25vw, 17px);\n      line-height: 1.7;\n      font-weight: 300;\n      color: var(--body-text);\n    }\n\n    .ols-note-card strong,\n    .ols-related-card strong,\n    .ols-faq-card strong {\n      font-weight: 750;\n      color: var(--navy);\n    }\n\n    .ols-note-card ul,\n    .ols-note-card ol {\n      margin: 0;\n      padding-left: 22px;\n    }\n\n    .ols-key-box {\n      margin-top: 20px;\n      background: #ffffff;\n      border: 1px solid rgba(37, 99, 235, 0.20);\n      border-left: 6px solid var(--blue);\n      border-radius: 18px;\n      padding: 18px 20px;\n    }\n\n    .ols-key-box p {\n      margin: 0;\n      font-weight: 400;\n      color: var(--navy);\n    }\n\n    .ols-process-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 14px;\n      margin-top: 22px;\n    }\n\n    .ols-process-step {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n      position: relative;\n    }\n\n    .ols-process-step span {\n      display: inline-grid;\n      place-items: center;\n      width: 34px;\n      height: 34px;\n      border-radius: 50%;\n      background: var(--blue);\n      color: #ffffff;\n      font-weight: 800;\n      margin-bottom: 12px;\n    }\n\n    .ols-process-step h3 {\n      margin: 0 0 8px;\n      font-size: 18px;\n      line-height: 1.25;\n      color: var(--navy);\n    }\n\n    .ols-process-step p {\n      margin: 0;\n      font-size: 14px;\n      line-height: 1.55;\n      color: var(--body-text);\n    }\n\n    .ols-figure-card {\n      margin: 26px 0 4px;\n      border: 1px solid var(--border);\n      border-radius: 26px;\n      overflow: visible;\n      background: #ffffff;\n      box-shadow: var(--inner-shadow);\n      position: relative;\n      z-index: 1;\n    }\n\n    .ols-figure-image {\n      width: 100%;\n      min-height: 320px;\n      display: flex;\n      align-items: center;\n      justify-content: center;\n      background: #ffffff;\n      padding: 20px;\n      border-radius: 26px 26px 0 0;\n      overflow: visible;\n      position: relative;\n      cursor: zoom-in;\n    }\n\n    .ols-figure-image::after {\n      content: \"Click to enlarge\";\n      position: absolute;\n      right: 14px;\n      bottom: 14px;\n      z-index: 3;\n      padding: 8px 12px;\n      border-radius: 999px;\n      background: rgba(28, 36, 75, 0.88);\n      color: #ffffff;\n      font-size: 12px;\n      line-height: 1;\n      font-weight: 800;\n      opacity: 0;\n      transform: translateY(6px);\n      transition: opacity 0.22s ease, transform 0.22s ease;\n      pointer-events: none;\n    }\n\n    .ols-figure-image:hover::after {\n      opacity: 1;\n      transform: translateY(0);\n    }\n\n    .ols-figure-image img {\n      max-width: 100%;\n      height: auto;\n      display: block;\n      cursor: zoom-in;\n      transition: transform 0.32s ease, box-shadow 0.32s ease, filter 0.32s ease;\n      transform-origin: center center;\n      will-change: transform;\n      position: relative;\n      z-index: 2;\n    }\n\n    @media (hover: hover) and (pointer: fine) {\n      .ols-figure-card .ols-figure-image:hover img {\n        transform: scale(1.5);\n        box-shadow: 0 30px 80px rgba(28, 36, 75, 0.28);\n        filter: saturate(1.05) contrast(1.03);\n      }\n\n      .ols-figure-card:hover {\n        z-index: 50;\n      }\n    }\n\n    .ols-figure-caption {\n      padding: 22px 26px 24px;\n      background: linear-gradient(135deg, #ffffff, #f8fbff);\n      border-top: 1px solid var(--border);\n      border-radius: 0 0 26px 26px;\n    }\n\n    .ols-figure-caption h3 {\n      margin: 0 0 8px;\n      color: var(--navy);\n      font-size: clamp(21px, 2vw, 28px);\n      line-height: 1.25;\n      font-weight: 800;\n      font-style: italic;\n    }\n\n    .ols-figure-caption p {\n      margin: 0;\n      color: #5f6b85;\n      font-size: clamp(15px, 1.2vw, 17px);\n      line-height: 1.6;\n      font-weight: 300;\n      font-style: italic;\n    }\n\n    .ols-cp2-lightbox {\n      position: fixed;\n      inset: 0;\n      background: rgba(8, 13, 31, 0.88);\n      backdrop-filter: blur(6px);\n      z-index: 999999;\n      display: none;\n      align-items: center;\n      justify-content: center;\n      padding: 24px;\n    }\n\n    .ols-cp2-lightbox.is-open {\n      display: flex;\n    }\n\n    .ols-cp2-lightbox img {\n      max-width: min(96vw, 1500px);\n      max-height: 92vh;\n      width: auto;\n      height: auto;\n      display: block;\n      border-radius: 18px;\n      box-shadow: 0 30px 90px rgba(0, 0, 0, 0.38);\n      background: #ffffff;\n    }\n\n    .ols-cp2-lightbox button {\n      position: absolute;\n      top: 18px;\n      right: 18px;\n      width: 44px;\n      height: 44px;\n      border-radius: 999px;\n      border: 1px solid rgba(255, 255, 255, 0.35);\n      background: #ffffff;\n      color: var(--navy);\n      font-family: Poppins, Arial, sans-serif;\n      font-size: 26px;\n      line-height: 1;\n      cursor: pointer;\n      font-weight: 800;\n      box-shadow: 0 14px 36px rgba(0, 0, 0, 0.24);\n    }\n\n    .ols-cp2-lightbox button:hover {\n      background: var(--soft-blue);\n    }\n\n    .ols-cp2-lightbox p {\n      position: absolute;\n      left: 28px;\n      right: 84px;\n      bottom: 16px;\n      margin: 0;\n      color: #ffffff;\n      font-size: 14px;\n      line-height: 1.4;\n    }\n\n    .ols-table-wrap {\n      overflow-x: auto;\n      border-radius: 22px;\n      border: 1px solid var(--border);\n      background: #ffffff;\n      margin-top: 18px;\n    }\n\n    .ols-table {\n      width: 100%;\n      border-collapse: collapse;\n      min-width: 680px;\n    }\n\n    .ols-table th {\n      background: var(--navy);\n      color: #ffffff;\n      padding: 15px 16px;\n      text-align: left;\n      font-size: 15px;\n      font-weight: 700;\n      vertical-align: top;\n    }\n\n    .ols-table td {\n      padding: 15px 16px;\n      border-bottom: 1px solid var(--border);\n      font-size: 15px;\n      line-height: 1.55;\n      color: var(--body-text);\n      vertical-align: top;\n    }\n\n    .ols-table tr:last-child td {\n      border-bottom: none;\n    }\n\n    .ols-highlight-row {\n      background: var(--soft-green);\n      font-weight: 650;\n    }\n\n    .ols-apparatus-grid {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 20px;\n    }\n\n    .ols-apparatus-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-apparatus-card h3 {\n      margin: 0 0 8px;\n      font-size: 19px;\n      color: var(--navy);\n    }\n\n    .ols-apparatus-card p {\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.6;\n    }\n\n    .ols-calculation-ladder {\n      display: grid;\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-calc-step {\n      display: grid;\n      grid-template-columns: 52px minmax(0, 1fr);\n      gap: 16px;\n      align-items: start;\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-calc-step-number {\n      width: 44px;\n      height: 44px;\n      border-radius: 14px;\n      background: var(--navy);\n      color: #ffffff;\n      display: grid;\n      place-items: center;\n      font-weight: 800;\n      font-size: 18px;\n    }\n\n    .ols-calc-step h3 {\n      margin: 0 0 8px;\n      font-size: 20px;\n      color: var(--navy);\n    }\n\n    .ols-calc-step p {\n      margin: 0 0 8px;\n    }\n\n    .ols-equation {\n      display: block;\n      width: fit-content;\n      max-width: 100%;\n      overflow-x: auto;\n      background: #f8fbff;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      border-radius: 14px;\n      padding: 10px 13px;\n      color: var(--navy);\n      font-weight: 700;\n      line-height: 1.7;\n      margin-top: 8px;\n      white-space: nowrap;\n    }\n\n    .ols-interactive-card {\n      background: radial-gradient(circle at top right, rgba(37, 99, 235, 0.14), transparent 32%), linear-gradient(135deg, #ffffff 0%, #f7f0ff 100%);\n      border: 1px solid var(--border);\n      border-radius: 30px;\n      box-shadow: var(--shadow);\n      padding: 34px;\n      margin: 0 0 24px;\n      overflow: hidden;\n    }\n\n    .ols-interactive-head {\n      display: flex;\n      align-items: flex-start;\n      justify-content: space-between;\n      gap: 18px;\n      margin-bottom: 22px;\n    }\n\n    .ols-interactive-head h2 {\n      margin: 0 0 10px;\n      font-size: clamp(28px, 3.4vw, 42px);\n      line-height: 1.12;\n      letter-spacing: -0.03em;\n      color: #111827;\n    }\n\n    .ols-interactive-head p {\n      margin: 0;\n      font-size: 16px;\n      line-height: 1.65;\n      color: var(--body-text);\n      font-weight: 300;\n    }\n\n    .ols-reset-btn,\n    .ols-action-btn {\n      appearance: none;\n      border: none;\n      border-radius: 999px;\n      padding: 12px 16px;\n      font-family: Poppins, Arial, sans-serif;\n      font-size: 14px;\n      font-weight: 750;\n      cursor: pointer;\n      transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;\n    }\n\n    .ols-reset-btn {\n      background: #ffffff;\n      color: var(--navy);\n      border: 1px solid var(--border);\n      flex-shrink: 0;\n    }\n\n    .ols-reset-btn:hover,\n    .ols-action-btn:hover {\n      transform: translateY(-2px);\n    }\n\n    .ols-interactive-grid {\n      display: grid;\n      grid-template-columns: minmax(0, 1.1fr) minmax(280px, 0.9fr);\n      gap: 18px;\n      align-items: start;\n    }\n\n    .ols-interactive-panel {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 22px;\n      padding: 20px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-interactive-panel h3 {\n      margin: 0 0 12px;\n      font-size: 22px;\n      color: var(--navy);\n    }\n\n    .ols-action-stack {\n      display: grid;\n      gap: 10px;\n    }\n\n    .ols-action-btn {\n      width: 100%;\n      text-align: left;\n      background: #ffffff;\n      color: var(--navy);\n      border: 1px solid rgba(37, 99, 235, 0.22);\n      box-shadow: 0 8px 16px rgba(28, 36, 75, 0.06);\n    }\n\n    .ols-action-btn.is-active {\n      background: var(--navy);\n      color: #ffffff;\n      border-color: var(--navy);\n    }\n\n    .ols-action-btn.is-pulse {\n      animation: olsCp4Pulse 1.7s infinite;\n    }\n\n    @keyframes olsCp4Pulse {\n      0% { box-shadow: 0 8px 16px rgba(28, 36, 75, 0.06), 0 0 0 0 rgba(37, 99, 235, 0.30); }\n      70% { box-shadow: 0 8px 16px rgba(28, 36, 75, 0.06), 0 0 0 10px rgba(37, 99, 235, 0.00); }\n      100% { box-shadow: 0 8px 16px rgba(28, 36, 75, 0.06), 0 0 0 0 rgba(37, 99, 235, 0.00); }\n    }\n\n    .ols-mini-results {\n      width: 100%;\n      border-collapse: collapse;\n      margin-top: 10px;\n      font-size: 14px;\n    }\n\n    .ols-mini-results th,\n    .ols-mini-results td {\n      border-bottom: 1px solid var(--border);\n      padding: 9px 7px;\n      text-align: left;\n      color: var(--body-text);\n    }\n\n    .ols-mini-results th {\n      color: var(--navy);\n      font-weight: 800;\n    }\n\n    .ols-mini-results tr.is-concordant td {\n      background: var(--soft-green);\n      color: var(--navy);\n      font-weight: 700;\n    }\n\n    .ols-hidden-value {\n      color: #98a2b3;\n      font-weight: 500;\n    }\n\n    .ols-visible-value {\n      color: var(--navy);\n      font-weight: 800;\n    }\n\n    .ols-working-box {\n      background: #f8fbff;\n      border: 1px solid rgba(37, 99, 235, 0.18);\n      border-radius: 18px;\n      padding: 16px;\n      min-height: 214px;\n    }\n\n    .ols-working-box h4 {\n      margin: 0 0 10px;\n      font-size: 19px;\n      color: var(--navy);\n    }\n\n    .ols-working-box p {\n      margin: 0 0 10px;\n      font-size: 15px;\n      line-height: 1.65;\n      color: var(--body-text);\n    }\n\n    .ols-answer-pill {\n      display: inline-flex;\n      align-items: center;\n      gap: 8px;\n      padding: 10px 13px;\n      border-radius: 999px;\n      background: var(--soft-green);\n      color: var(--navy);\n      font-weight: 800;\n      border: 1px solid rgba(63, 143, 70, 0.25);\n      margin-top: 6px;\n    }\n\n    .ols-error-grid {\n      display: grid;\n      grid-template-columns: repeat(2, minmax(0, 1fr));\n      gap: 14px;\n      margin-top: 20px;\n    }\n\n    .ols-error-card {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 20px;\n      padding: 18px;\n      box-shadow: var(--inner-shadow);\n    }\n\n    .ols-error-card h3 {\n      margin: 0 0 8px;\n      font-size: 18px;\n      color: var(--navy);\n    }\n\n    .ols-error-card p {\n      margin: 0;\n      font-size: 15px;\n      line-height: 1.6;\n    }\n\n    .ols-related-grid {\n      display: grid;\n      grid-template-columns: repeat(3, minmax(0, 1fr));\n      gap: 16px;\n      margin-top: 18px;\n    }\n\n    .ols-related-item {\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n      background: #ffffff;\n      color: var(--navy);\n      text-decoration: none;\n      font-weight: 700;\n      line-height: 1.45;\n      transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;\n    }\n\n    .ols-related-item:hover {\n      transform: translateY(-2px);\n      box-shadow: 0 10px 22px rgba(28, 36, 75, 0.08);\n      background: var(--soft-blue);\n    }\n\n    .ols-faq-list {\n      display: grid;\n      gap: 14px;\n      margin-top: 18px;\n    }\n\n    .ols-faq-item {\n      background: #ffffff;\n      border: 1px solid var(--border);\n      border-radius: 18px;\n      padding: 18px;\n    }\n\n    .ols-faq-item h3 {\n      margin: 0 0 8px;\n      font-size: 19px;\n      color: var(--navy);\n    }\n\n    .ols-faq-item p {\n      margin: 0;\n    }\n\n    @media (max-width: 1050px) {\n      .ols-process-grid,\n      .ols-related-grid {\n        grid-template-columns: repeat(2, minmax(0, 1fr));\n      }\n\n      .ols-interactive-grid {\n        grid-template-columns: 1fr;\n      }\n    }\n\n    @media (max-width: 760px) {\n      .ols-cp-shell {\n        padding: 14px 12px 44px;\n      }\n\n      .ols-title-card,\n      .ols-note-card,\n      .ols-related-card,\n      .ols-faq-card,\n      .ols-interactive-card {\n        padding: 24px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-note-title,\n      .ols-interactive-head {\n        align-items: flex-start;\n      }\n\n      .ols-interactive-head {\n        flex-direction: column;\n      }\n\n      .ols-reset-btn {\n        width: 100%;\n        text-align: center;\n      }\n\n      .ols-process-grid,\n      .ols-apparatus-grid,\n      .ols-error-grid,\n      .ols-related-grid {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-calc-step {\n        grid-template-columns: 1fr;\n      }\n\n      .ols-figure-card { border-radius: 22px; }\n\n      .ols-figure-image {\n        min-height: 240px;\n        padding: 14px;\n        border-radius: 22px 22px 0 0;\n      }\n\n      .ols-figure-caption {\n        padding: 18px;\n      }\n\n      .ols-cp2-lightbox {\n        padding: 12px;\n      }\n\n      .ols-cp2-lightbox p {\n        display: none;\n      }\n\n      .ols-author {\n        align-items: flex-start;\n        padding: 22px 18px;\n        border-radius: 22px;\n      }\n\n      .ols-author-avatar-img {\n        width: 72px;\n        height: 72px;\n      }\n\n      .ols-author-title {\n        font-size: 24px;\n      }\n\n      .ols-author-description {\n        font-size: 15px;\n      }\n    }\n  <\/style>\n\n  <div class=\"ols-cp-sidebar-shortcode\"><aside class=\"ols-sidebar\">\r\n  <div class=\"ols-sidebar-header\">\r\n    <h3>Revision Notes<\/h3>\r\n    <p>Edexcel A Level Chemistry<\/p>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Core Practicals<\/h4>\r\n    <ul class=\"ols-topic-list\">\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-1-molar-volume-of-a-gas\/\">CP1: Molar Volume of a Gas<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-2-prepare-a-standard-solution\/\">CP2: Prepare a Standard Solution<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-3-concentration-of-hcl-by-titration\/\">CP3: Concentration of HCl by Titration<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-4-hydrolysis-of-halogenoalkanes\/\">CP4: Hydrolysis of Halogenoalkanes<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-5-oxidation-of-ethanol\/\">CP5: Oxidation of Ethanol<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-6-chlorination-of-2-methylpropan-2-ol\/\">CP6: Chlorination of 2-methylpropan-2-ol<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-7-analysis-of-inorganic-and-organic-unknowns\/\">CP7: Analysis of Inorganic and Organic Unknowns<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-8-enthalpy-change-via-hess-law\/\">CP8: Enthalpy Change via Hess\u2019s Law<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-9-electrochemical-cells\/\">CP9: Electrochemical Cells<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-10-titration-of-edta\/\">CP10: Titration of EDTA<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-11-rates-of-reaction-clock\/\">CP11: Rates of Reaction (Clock)<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-12-continuous-monitoring-rates\/\">CP12: Continuous Monitoring Rates<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-13-preparation-of-aspirin\/\">CP13: Preparation of Aspirin<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-14-thin-layer-chromatography\/\">CP14: Thin Layer Chromatography<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-15-preparing-organic-compound\/\">CP15: Preparing Organic Compound<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/cp-16-testing-organic-unknowns\/\">CP16: Testing Organic Unknowns<\/a><\/li>\r\n    <\/ul>\r\n  <\/div>\r\n\r\n  <div class=\"ols-topic-group\">\r\n    <h4>Useful Links<\/h4>\r\n    <ul class=\"ols-topic-list\">\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\">Edexcel A Level Chemistry<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/\">Core Practicals<\/a><\/li>\r\n      <li><a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/topic-5-formulae-equations-and-amounts-of-substance\/\">Formulae, Equations and Amounts of Substance<\/a><\/li>\r\n    <\/ul>\r\n  <\/div>\r\n<\/aside>\r\n\r\n<script>\r\n(function () {\r\n  var sidebar = document.querySelector('.ols-sidebar');\r\n  if (!sidebar) return;\r\n\r\n  var currentPath = window.location.pathname.replace(\/\\\/$\/, '');\r\n\r\n  sidebar.querySelectorAll('.ols-topic-list li').forEach(function (li) {\r\n    li.classList.remove('active');\r\n\r\n    var link = li.querySelector('a');\r\n    if (!link) return;\r\n\r\n    var linkPath = new URL(link.href).pathname.replace(\/\\\/$\/, '');\r\n\r\n    if (linkPath === currentPath) {\r\n      li.classList.add('active');\r\n    }\r\n  });\r\n})();\r\n<\/script><\/div>\n\n  <div class=\"ols-cp-shell\">\n    <main class=\"ols-cp-main\">\n      <nav class=\"ols-breadcrumbs\" aria-label=\"Breadcrumb\">\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/\">Revision Notes<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/\">A Level Chemistry<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/\">Edexcel<\/a> \/\n        <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/revision-notes\/a-level-chemistry\/edexcel\/core-practicals\/\">Core Practicals<\/a> \/\n        <span>CP2: Prepare a Standard Solution<\/span>\n      <\/nav>\n\n      <header class=\"ols-title-card\">\n        <h1>CP2: Prepare a Standard Solution<\/h1>\n        <p class=\"ols-page-intro\">In this core practical, you prepare a standard solution of sulfamic acid from a solid sample, then use it in an acid-base titration to calculate the concentration of sodium hydroxide.<\/p>\n        <div class=\"ols-badges\">\n          <div class=\"ols-badge\">Exam board: Edexcel<\/div>\n          <div class=\"ols-badge\">Paper 3: General and Practical Principles in Chemistry\n<\/div>\n        <\/div>\n        <div class=\"ols-author\">\n          <img decoding=\"async\" class=\"ols-author-avatar-img\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Author-Profile.jpeg\" alt=\"Dr. Mohammed Al-Fatah\">\n\n          <div class=\"ols-author-content\">\n            <h2 class=\"ols-author-title\">Written by: Dr. Mohammed Al-Fatah<\/h2>\n            <p class=\"ols-author-description\">Chemistry specialist revision notes for 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\"><\/path>\n              <\/svg>\n              View LinkedIn Profile\n            <\/a>\n          <\/div>\n        <\/div>\n      <\/header>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">1<\/div>\n          <h2>What This Practical Is Testing<\/h2>\n        <\/div>\n        <p>The practical has two connected parts. First, you make a <strong>standard solution<\/strong> of sulfamic acid. A standard solution has a known concentration. Then, you use that acid in a titration to find the concentration of a sodium hydroxide solution.<\/p>\n        <p>The overall logic is: if the mass of sulfamic acid is known, the moles of acid are known. If the final volume in the volumetric flask is known, the concentration of the acid can be calculated. That acid can then be used to calculate the concentration of NaOH from the titre.<\/p>\n\n        <div class=\"ols-process-grid\" aria-label=\"CP2 practical process map\">\n          <div class=\"ols-process-step\">\n            <span>1<\/span>\n            <h3>Weigh the acid<\/h3>\n            <p>Find the accurate mass of sulfamic acid transferred.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>2<\/span>\n            <h3>Make the solution<\/h3>\n            <p>Dissolve, transfer with washings, make up to 250 cm<sup>3<\/sup>.<\/p>\n          <\/div>\n          <div class=\"ols-process-step\">\n            <span>3<\/span>\n            <h3>Titrate NaOH<\/h3>\n            <p>Use the acid in the burette against 25.0 cm<sup>3<\/sup> sodium hydroxide.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Key idea:<\/strong> CP2 links accurate practical technique to quantitative chemistry. Every rinse, reading and volume affects the final concentration.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">2<\/div>\n          <h2>Safety and Apparatus<\/h2>\n        <\/div>\n        <p>Sodium hydroxide is hazardous to the eyes, so eye protection is required. Avoid skin contact with both sulfamic acid and sodium hydroxide. Take care when clamping and filling the burette because it can crack or topple over.<\/p>\n\n        <div class=\"ols-apparatus-grid\">\n          <div class=\"ols-apparatus-card\">\n            <h3>Making the standard solution<\/h3>\n            <p>Solid sulfamic acid, 250 cm<sup>3<\/sup> beaker, distilled water, funnel, 250 cm<sup>3<\/sup> volumetric flask and a 2 d.p. balance.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Carrying out the titration<\/h3>\n            <p>Burette, clamp and stand, 25.0 cm<sup>3<\/sup> volumetric pipette with safety filler, 250 cm<sup>3<\/sup> conical flask, sodium hydroxide and methyl orange.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card green\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">3<\/div>\n          <h2>Preparing the Standard Solution<\/h2>\n        <\/div>\n        <p>Start by weighing an empty test tube or weighing bottle. Add about 2.5 g of sulfamic acid, then reweigh the container and contents. The difference between the two masses gives the accurate mass of solid used.<\/p>\n        <p>Dissolve the sulfamic acid in about 100 cm<sup>3<\/sup> of distilled water in a beaker. Transfer the solution to a 250 cm<sup>3<\/sup> volumetric flask. Rinse the beaker, funnel and glass rod, then add the washings to the volumetric flask so that no acid is lost.<\/p>\n        <p>Finally, add distilled water until the bottom of the meniscus sits on the calibration mark. Stopper the flask and invert it several times to make the concentration uniform throughout the solution.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Technique<\/th>\n                <th>Why it is done<\/th>\n                <th>What can go wrong<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td><strong>Reweigh the empty container<\/strong><\/td>\n                <td>Finds the mass of solid actually transferred.<\/td>\n                <td>Assuming the starting mass was fully transferred can give an inaccurate mole value.<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>Rinse the beaker and funnel<\/strong><\/td>\n                <td>Transfers any remaining acid into the volumetric flask.<\/td>\n                <td>Losing acid lowers the number of moles in the final solution.<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>Make up to the mark carefully<\/strong><\/td>\n                <td>Gives the exact final volume needed for the concentration calculation.<\/td>\n                <td>Going above the mark makes the acid too dilute.<\/td>\n              <\/tr>\n              <tr>\n                <td><strong>Invert the flask<\/strong><\/td>\n                <td>Makes the solution uniform.<\/td>\n                <td>Poor mixing means different parts of the solution may have different concentrations.<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Preparing-a-solution-stepbystep-guide.webp\" alt=\"Preparing a standard solution step-by-step guide showing weighing, dissolving, transferring, making up to volume and mixing.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Preparing a standard solution from a solid<\/h3>\n            <p>Use this sequence to revise the practical method: weigh accurately, dissolve fully, transfer with washings, make up to the mark, then invert to mix.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">4<\/div>\n          <h2>Using the Volumetric Flask Correctly<\/h2>\n        <\/div>\n        <p>A volumetric flask has one calibration mark on its neck. This mark shows the exact volume the flask is designed to contain. In this practical, the solution is made up to <strong>250 cm<sup>3<\/sup><\/strong>.<\/p>\n        <p>The bottom of the meniscus should sit on the calibration line. Use a dropping pipette for the last few drops because it is easy to overshoot the line if you add water too quickly.<\/p>\n        <p>Do not heat the volumetric flask or pour hot solution into it. Heat can expand the glass, changing the volume and making the concentration inaccurate.<\/p>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Exam wording:<\/strong> Say \u201cmake up to the mark with distilled water\u201d rather than \u201cfill it up\u201d. The mark is what makes the volume accurate.<\/p>\n        <\/div>\n\n        <div class=\"ols-figure-card\">\n          <div class=\"ols-figure-image\">\n            <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/06\/Using-a-volumetric-flask-correctly-1.webp\" alt=\"Using a 250 cm3 volumetric flask correctly with calibration mark, meniscus guidance and mass measurement advice.\">\n          <\/div>\n          <div class=\"ols-figure-caption\">\n            <h3>Volumetric flask technique<\/h3>\n            <p>The calibration mark, meniscus position and mixing step are essential because the concentration calculation depends on the final volume being correct.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card purple\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">5<\/div>\n          <h2>Carrying Out the Titration<\/h2>\n        <\/div>\n        <p>After preparing the sulfamic acid solution, use it to titrate sodium hydroxide. The <strong>burette contains the sulfamic acid<\/strong>. The <strong>conical flask contains 25.0 cm<sup>3<\/sup> of sodium hydroxide<\/strong> measured using a volumetric pipette.<\/p>\n        <p>Add methyl orange indicator to the sodium hydroxide in the conical flask. Run acid from the burette into the flask until the end point is reached. Burette readings should be recorded to the nearest <strong>0.05 cm<sup>3<\/sup><\/strong>.<\/p>\n\n        <div class=\"ols-apparatus-grid\">\n          <div class=\"ols-apparatus-card\">\n            <h3>Burette<\/h3>\n            <p>Contains the standard sulfamic acid solution you prepared.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Pipette<\/h3>\n            <p>Measures a fixed 25.0 cm<sup>3<\/sup> aliquot of sodium hydroxide.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>Conical flask<\/h3>\n            <p>Contains sodium hydroxide and methyl orange indicator.<\/p>\n          <\/div>\n          <div class=\"ols-apparatus-card\">\n            <h3>End point<\/h3>\n            <p>Near the end point, add acid dropwise and swirl continuously.<\/p>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Technique point:<\/strong> Rinse the pipette with sodium hydroxide after washing it with water. Any water left inside the pipette would dilute the sodium hydroxide and change the moles transferred.<\/p>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">6<\/div>\n          <h2>From Burette Readings to Titres<\/h2>\n        <\/div>\n        <p>A titre is calculated from:<\/p>\n        <span class=\"ols-equation\">titre = final burette reading &#8211; initial burette reading<\/span>\n        <p>Only concordant titres should be used to calculate the mean titre. In this sample data, trials 2 and 4 are concordant because they both give 20.05 cm<sup>3<\/sup>.<\/p>\n\n        <div class=\"ols-table-wrap\">\n          <table class=\"ols-table\">\n            <thead>\n              <tr>\n                <th>Trial<\/th>\n                <th>Final burette reading \/ cm<sup>3<\/sup><\/th>\n                <th>Initial burette reading \/ cm<sup>3<\/sup><\/th>\n                <th>Titre \/ cm<sup>3<\/sup><\/th>\n                <th>Use in mean?<\/th>\n              <\/tr>\n            <\/thead>\n            <tbody>\n              <tr>\n                <td>Trial 1<\/td>\n                <td>21.00<\/td>\n                <td>0.25<\/td>\n                <td>20.75<\/td>\n                <td>No<\/td>\n              <\/tr>\n              <tr class=\"ols-highlight-row\">\n                <td>Trial 2<\/td>\n                <td>41.05<\/td>\n                <td>21.00<\/td>\n                <td>20.05<\/td>\n                <td>Yes<\/td>\n              <\/tr>\n              <tr>\n                <td>Trial 3<\/td>\n                <td>20.85<\/td>\n                <td>0.50<\/td>\n                <td>20.35<\/td>\n                <td>No<\/td>\n              <\/tr>\n              <tr class=\"ols-highlight-row\">\n                <td>Trial 4<\/td>\n                <td>40.90<\/td>\n                <td>20.85<\/td>\n                <td>20.05<\/td>\n                <td>Yes<\/td>\n              <\/tr>\n            <\/tbody>\n          <\/table>\n        <\/div>\n\n        <div class=\"ols-key-box\">\n          <p><strong>Mean titre:<\/strong> (20.05 + 20.05) \u00f7 2 = 20.05 cm<sup>3<\/sup><\/p>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-interactive-card\" aria-label=\"Interactive CP2 calculation walkthrough\">\n        <div class=\"ols-interactive-head\">\n          <div>\n            <h2>Interactive: Build the CP2 Calculation<\/h2>\n            <p>Work through the data in order. The aim is to connect the practical readings to the final concentration of sodium hydroxide.<\/p>\n          <\/div>\n          <button type=\"button\" class=\"ols-reset-btn\" id=\"olsCp4Reset\">Reset<\/button>\n        <\/div>\n\n        <div class=\"ols-interactive-grid\">\n          <div class=\"ols-interactive-panel\">\n            <h3>Sample results<\/h3>\n            <p><strong>Mass of sulfamic acid:<\/strong> 2.41 g<\/p>\n            <table class=\"ols-mini-results\" aria-label=\"Interactive sample titration results\">\n              <thead>\n                <tr>\n                  <th>Trial<\/th>\n                  <th>Final<\/th>\n                  <th>Initial<\/th>\n                  <th>Titre<\/th>\n                <\/tr>\n              <\/thead>\n              <tbody>\n                <tr id=\"olsCp4Row1\"><td>1<\/td><td>21.00<\/td><td>0.25<\/td><td><span class=\"ols-hidden-value\" data-titre=\"20.75\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp4Row2\"><td>2<\/td><td>41.05<\/td><td>21.00<\/td><td><span class=\"ols-hidden-value\" data-titre=\"20.05\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp4Row3\"><td>3<\/td><td>20.85<\/td><td>0.50<\/td><td><span class=\"ols-hidden-value\" data-titre=\"20.35\">?<\/span><\/td><\/tr>\n                <tr id=\"olsCp4Row4\"><td>4<\/td><td>40.90<\/td><td>20.85<\/td><td><span class=\"ols-hidden-value\" data-titre=\"20.05\">?<\/span><\/td><\/tr>\n              <\/tbody>\n            <\/table>\n          <\/div>\n\n          <div class=\"ols-interactive-panel\">\n            <h3>Walkthrough controls<\/h3>\n            <div class=\"ols-action-stack\">\n              <button type=\"button\" class=\"ols-action-btn is-pulse\" data-step=\"1\">1. Calculate the titres<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"2\">2. Identify concordant titres<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"3\">3. Calculate mean titre<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"4\">4. Calculate acid concentration<\/button>\n              <button type=\"button\" class=\"ols-action-btn\" data-step=\"5\">5. Calculate NaOH concentration<\/button>\n            <\/div>\n          <\/div>\n        <\/div>\n\n        <div class=\"ols-interactive-panel\" style=\"margin-top:18px;\">\n          <div class=\"ols-working-box\" id=\"olsCp4Working\">\n            <h4>Start here<\/h4>\n            <p>Click the first button to calculate each titre from the final and initial burette readings.<\/p>\n            <p class=\"ols-equation\">titre = final reading &#8211; initial reading<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n\n      <article class=\"ols-note-card gold\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">7<\/div>\n          <h2>Worked Calculation Ladder<\/h2>\n        <\/div>\n        <p>This worked example uses the sample data above. The mass of sulfamic acid is 2.41 g and the mean titre is 20.05 cm<sup>3<\/sup>.<\/p>\n\n        <div class=\"ols-calculation-ladder\">\n          <div class=\"ols-calc-step\">\n            <div class=\"ols-calc-step-number\">1<\/div>\n            <div>\n              <h3>Calculate moles of sulfamic acid made<\/h3>\n              <p>Use the mass and M<sub>r<\/sub> of sulfamic acid, 97.1.<\/p>\n              <span class=\"ols-equation\">n = m \u00f7 M<sub>r<\/sub> = 2.41 \u00f7 97.1 = 0.0248 mol<\/span>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-calc-step\">\n            <div class=\"ols-calc-step-number\">2<\/div>\n            <div>\n              <h3>Calculate concentration of sulfamic acid<\/h3>\n              <p>The solution was made up to 250 cm<sup>3<\/sup>, which is 0.250 dm<sup>3<\/sup>.<\/p>\n              <span class=\"ols-equation\">c = n \u00f7 V = 0.0248 \u00f7 0.250 = 0.0993 mol dm<sup>-3<\/sup><\/span>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-calc-step\">\n            <div class=\"ols-calc-step-number\">3<\/div>\n            <div>\n              <h3>Calculate moles of acid in the mean titre<\/h3>\n              <p>The mean titre is 20.05 cm<sup>3<\/sup>, which is 0.02005 dm<sup>3<\/sup>.<\/p>\n              <span class=\"ols-equation\">n = cV = 0.0993 \u00d7 0.02005 = 0.00199 mol<\/span>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-calc-step\">\n            <div class=\"ols-calc-step-number\">4<\/div>\n            <div>\n              <h3>Use the mole ratio<\/h3>\n              <p>Sulfamic acid is monoprotic, so it reacts with sodium hydroxide in a 1:1 ratio.<\/p>\n              <span class=\"ols-equation\">n(NaOH) = n(sulfamic acid) = 0.00199 mol<\/span>\n            <\/div>\n          <\/div>\n\n          <div class=\"ols-calc-step\">\n            <div class=\"ols-calc-step-number\">5<\/div>\n            <div>\n              <h3>Calculate concentration of sodium hydroxide<\/h3>\n              <p>The volume of NaOH in the conical flask is 25.0 cm<sup>3<\/sup>, which is 0.0250 dm<sup>3<\/sup>.<\/p>\n              <span class=\"ols-equation\">c = n \u00f7 V = 0.00199 \u00f7 0.0250 = 0.0796 mol dm<sup>-3<\/sup><\/span>\n            <\/div>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <article class=\"ols-note-card soft\">\n        <div class=\"ols-note-title\">\n          <div class=\"ols-note-icon\">8<\/div>\n          <h2>Common Exam Mistakes<\/h2>\n        <\/div>\n        <div class=\"ols-error-grid\">\n          <div class=\"ols-error-card\">\n            <h3>Forgetting cm<sup>3<\/sup> to dm<sup>3<\/sup><\/h3>\n            <p>Divide cm<sup>3<\/sup> by 1000 before using c = n \u00f7 V.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Using every titre<\/h3>\n            <p>Use concordant titres only. Ignore rough or non-concordant values when calculating the mean.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Not adding washings<\/h3>\n            <p>If acid remains in the beaker or funnel, fewer moles reach the volumetric flask.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Filling above the mark<\/h3>\n            <p>Adding too much water makes the acid solution more dilute, so a larger titre would be needed.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Too much indicator<\/h3>\n            <p>Indicators are weak acids. Adding too much indicator can reduce the accuracy of the titration.<\/p>\n          <\/div>\n          <div class=\"ols-error-card\">\n            <h3>Drying the conical flask unnecessarily<\/h3>\n            <p>Water in the conical flask does not change the moles of NaOH because the NaOH was measured before being added.<\/p>\n          <\/div>\n        <\/div>\n      <\/article>\n\n      <section class=\"ols-faq-card\">\n        <h2>CP2 Exam Questions Students Should Be Ready For<\/h2>\n        <div class=\"ols-faq-list\">\n          <div class=\"ols-faq-item\">\n            <h3>Why is a volumetric flask used instead of a measuring cylinder?<\/h3>\n            <p>A volumetric flask is more accurate because it is calibrated to contain one exact volume.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why should the pipette be rinsed with sodium hydroxide?<\/h3>\n            <p>Any water left in the pipette would dilute the sodium hydroxide, changing the number of moles transferred into the conical flask.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>Why does water in the conical flask not matter?<\/h3>\n            <p>The moles of sodium hydroxide are fixed by the 25.0 cm<sup>3<\/sup> pipetted volume. Extra water only dilutes the solution in the flask, but it does not change the moles present.<\/p>\n          <\/div>\n          <div class=\"ols-faq-item\">\n            <h3>What happens if the volumetric flask is filled above the mark?<\/h3>\n            <p>The acid becomes too dilute. A larger titre would be required to neutralise the same amount of sodium hydroxide.<\/p>\n          <\/div>\n        <\/div>\n      <\/section>\n    <\/main>\n  <\/div>\n\n  <script>\n    (function(){\n      var root = document.querySelector('.ols-cp2-standard-solution-page');\n      if (!root) return;\n\n      var working = root.querySelector('#olsCp4Working');\n      var reset = root.querySelector('#olsCp4Reset');\n      var buttons = Array.prototype.slice.call(root.querySelectorAll('.ols-action-btn'));\n      var titreSpans = Array.prototype.slice.call(root.querySelectorAll('[data-titre]'));\n      var row2 = root.querySelector('#olsCp4Row2');\n      var row4 = root.querySelector('#olsCp4Row4');\n\n      var content = {\n        1: '<h4>Step 1: Calculate the titres<\/h4><p>Subtract the initial burette reading from the final burette reading.<\/p><p class=\"ols-equation\">Trial 1: 21.00 - 0.25 = 20.75 cm<sup>3<\/sup><\/p><p class=\"ols-equation\">Trial 2: 41.05 - 21.00 = 20.05 cm<sup>3<\/sup><\/p><p class=\"ols-equation\">Trial 3: 20.85 - 0.50 = 20.35 cm<sup>3<\/sup><\/p><p class=\"ols-equation\">Trial 4: 40.90 - 20.85 = 20.05 cm<sup>3<\/sup><\/p>',\n        2: '<h4>Step 2: Identify the concordant titres<\/h4><p>Trials 2 and 4 are concordant because they match exactly.<\/p><p class=\"ols-equation\">20.05 cm<sup>3<\/sup> and 20.05 cm<sup>3<\/sup><\/p><span class=\"ols-answer-pill\">Use trials 2 and 4<\/span>',\n        3: '<h4>Step 3: Calculate the mean titre<\/h4><p>Use the concordant titres only.<\/p><p class=\"ols-equation\">mean titre = (20.05 + 20.05) \u00f7 2<\/p><span class=\"ols-answer-pill\">Mean titre = 20.05 cm<sup>3<\/sup><\/span>',\n        4: '<h4>Step 4: Calculate the acid concentration<\/h4><p>First find moles of sulfamic acid from the mass, then divide by the 250 cm<sup>3<\/sup> volume.<\/p><p class=\"ols-equation\">n = 2.41 \u00f7 97.1 = 0.0248 mol<\/p><p class=\"ols-equation\">c = 0.0248 \u00f7 0.250 = 0.0993 mol dm<sup>-3<\/sup><\/p><span class=\"ols-answer-pill\">Acid concentration = 0.0993 mol dm<sup>-3<\/sup><\/span>',\n        5: '<h4>Step 5: Calculate the NaOH concentration<\/h4><p>The mean titre is 20.05 cm<sup>3<\/sup>, or 0.02005 dm<sup>3<\/sup>. Sulfamic acid reacts 1:1 with NaOH.<\/p><p class=\"ols-equation\">n(acid) = 0.0993 \u00d7 0.02005 = 0.00199 mol<\/p><p class=\"ols-equation\">c(NaOH) = 0.00199 \u00f7 0.0250 = 0.0796 mol dm<sup>-3<\/sup><\/p><span class=\"ols-answer-pill\">NaOH concentration = 0.0796 mol dm<sup>-3<\/sup><\/span>'\n      };\n\n      function setActive(step) {\n        buttons.forEach(function(btn){\n          var btnStep = btn.getAttribute('data-step');\n          btn.classList.toggle('is-active', btnStep === String(step));\n          btn.classList.remove('is-pulse');\n        });\n\n        var next = root.querySelector('[data-step=\"' + (Number(step) + 1) + '\"]');\n        if (next) next.classList.add('is-pulse');\n\n        if (working && content[step]) {\n          working.innerHTML = content[step];\n        }\n\n        if (step >= 1) {\n          titreSpans.forEach(function(span){\n            span.textContent = span.getAttribute('data-titre');\n            span.className = 'ols-visible-value';\n          });\n        }\n\n        if (step >= 2) {\n          if (row2) row2.classList.add('is-concordant');\n          if (row4) row4.classList.add('is-concordant');\n        }\n      }\n\n      buttons.forEach(function(btn){\n        btn.addEventListener('click', function(){\n          setActive(btn.getAttribute('data-step'));\n        });\n      });\n\n      if (reset) {\n        reset.addEventListener('click', function(){\n          titreSpans.forEach(function(span){\n            span.textContent = '?';\n            span.className = 'ols-hidden-value';\n          });\n          if (row2) row2.classList.remove('is-concordant');\n          if (row4) row4.classList.remove('is-concordant');\n          buttons.forEach(function(btn, index){\n            btn.classList.remove('is-active');\n            btn.classList.toggle('is-pulse', index === 0);\n          });\n          if (working) {\n            working.innerHTML = '<h4>Start here<\/h4><p>Click the first button to calculate each titre from the final and initial burette readings.<\/p><p class=\"ols-equation\">titre = final reading - initial reading<\/p>';\n          }\n        });\n      }\n    })();\n  <\/script>\n\n  <div class=\"ols-cp2-lightbox\" id=\"olsCp2Lightbox\" aria-hidden=\"true\">\n    <button type=\"button\" aria-label=\"Close image\">&times;<\/button>\n    <img decoding=\"async\" src=\"\" alt=\"\">\n    <p><\/p>\n  <\/div>\n\n  <script>\n    (function(){\n      function initCp2Lightbox(){\n        var page = document.getElementById('ols-cp2-page');\n        if (!page) { return; 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