{"id":237854,"date":"2025-06-17T17:22:42","date_gmt":"2025-06-17T17:22:42","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=237854"},"modified":"2025-06-17T17:22:44","modified_gmt":"2025-06-17T17:22:44","slug":"calculated-ph-x-i-x-quadratic-measured-ph-ph-paper-10-5-2-99-3-31-3-82-weak-acid-base-molarity","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/17\/calculated-ph-x-i-x-quadratic-measured-ph-ph-paper-10-5-2-99-3-31-3-82-weak-acid-base-molarity\/","title":{"rendered":"Calculated pH: X-I-X quadratic Measured pH: PH paper 10.5, 2.99, 3.31, 3.82 Weak Acid-Base Molarity"},"content":{"rendered":"\n

Calculated pH: X-I-X quadratic Measured pH: PH paper 10.5, 2.99, 3.31, 3.82 Weak Acid-Base Molarity: 0.0010 M NH4OH 0.0010 M CH3COOH 0.010 M CH3COOH 0.01 M CH3COOH 0.0010 M CH3COOH 0.0010 M CH3COOH 0.00010 M CH3COOH 0.0001 M CH3COOH 0.0001 M CH3COOH Salts Molarity: 0.1 M NaCl 0.1 M NaCH3COO 0.1 M NH4CH3COO 0.1 M NH4CH3COO 0.1 M NaHCO3 0.1 M Na2CO3 Calculated pH: 0.10 M NaCl – 8.81 0.10 M NaCH3COO – 7.02 0.10 M NH4CH3COO – 9.62 0.10 M NaHCO3 – 4.80E-11 0.10 M Na2CO3 – 2.40E-08 0.10 M Na2CO3 – 2.10E-04 Buffer Molarity: CH3COOH\/NaCH3COO – 1.80E-05 Calculated pH: 4.69 Measured pH: 4.12 pH after 30 drops of HCl: 5.31 pH after 30 drops of NaOH: 4.12<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n

Correct Answer and Key Observations:<\/strong><\/p>\n\n\n\n

    \n
  1. Weak Acid-Base Solutions:<\/strong>\n
      \n
    • For weak acid solutions such as acetic acid (CH\u2083COOH), pH increases as the molarity decreases. This is consistent with dilution reducing the concentration of hydrogen ions.<\/li>\n\n\n\n
    • Example: 0.010 M CH\u2083COOH has a higher hydrogen ion concentration than 0.0001 M CH\u2083COOH, thus its pH will be lower.<\/li>\n\n\n\n
    • NH\u2084OH, a weak base, at 0.0010 M should yield a pH slightly above 7. The value 10.5 is consistent with this weak basic behavior.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Salt Solutions:<\/strong>\n
        \n
      • NaCl<\/strong> is a neutral salt from a strong acid and base. The calculated pH of 8.81 seems slightly high, possibly due to water purity or instrumentation error, as NaCl alone should yield pH \u2248 7.<\/li>\n\n\n\n
      • NaCH\u2083COO<\/strong> results from a strong base and weak acid, producing a basic solution. A pH of 7.02 is consistent with this.<\/li>\n\n\n\n
      • NH\u2084CH\u2083COO<\/strong> is a salt of a weak acid and weak base. The calculated pH of 9.62 indicates the basic component dominates.<\/li>\n\n\n\n
      • NaHCO\u2083<\/strong> and Na\u2082CO\u2083<\/strong> are basic due to the carbonate and bicarbonate ions. The extremely low calculated values (e.g., 4.80E-11) likely represent [H\u207a], not pH. Converting gives pH \u2248 10.3 and 7.6, respectively.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Buffer System:<\/strong>\n
          \n
        • A buffer made from CH\u2083COOH and NaCH\u2083COO should resist changes in pH when small amounts of acid or base are added.<\/li>\n\n\n\n
        • The measured pH of 4.12 vs. calculated 4.69 shows that the actual buffer was slightly more acidic.<\/li>\n\n\n\n
        • After 30 drops of HCl, the buffer\u2019s pH increased to 5.31, possibly due to a mislabeling or unexpected chemical behavior. Normally, acid addition should decrease pH.<\/li>\n\n\n\n
        • After 30 drops of NaOH, the pH returned to 4.12, which also indicates possible experimental inconsistency.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
          \n\n\n\n

          Conclusion:<\/strong>
          This data aligns generally with acid-base and buffer theory. Discrepancies between calculated and measured values can stem from experimental error, concentration inaccuracies, or instrumentation limitations like pH paper precision.<\/p>\n\n\n\n

          \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

          Calculated pH: X-I-X quadratic Measured pH: PH paper 10.5, 2.99, 3.31, 3.82 Weak Acid-Base Molarity: 0.0010 M NH4OH 0.0010 M CH3COOH 0.010 M CH3COOH 0.01 M CH3COOH 0.0010 M CH3COOH 0.0010 M CH3COOH 0.00010 M CH3COOH 0.0001 M CH3COOH 0.0001 M CH3COOH Salts Molarity: 0.1 M NaCl 0.1 M NaCH3COO 0.1 M NH4CH3COO 0.1 M […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-237854","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/237854","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=237854"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/237854\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=237854"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=237854"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=237854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}