{"id":233022,"date":"2025-06-12T13:11:08","date_gmt":"2025-06-12T13:11:08","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=233022"},"modified":"2025-06-12T13:11:10","modified_gmt":"2025-06-12T13:11:10","slug":"sodium-benzoate-c6h5coona-is-a-product-of-sodium-hydroxide-and-benzoic-acid-c6h5cooh-ka-6-310-5","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/12\/sodium-benzoate-c6h5coona-is-a-product-of-sodium-hydroxide-and-benzoic-acid-c6h5cooh-ka-6-310-5\/","title":{"rendered":"Sodium benzoate (C6H5COONa) is a product of sodium hydroxide and benzoic acid (C6H5COOH) (ka = 6.3*10^-5)."},"content":{"rendered":"\n

Sodium benzoate (C6H5COONa) is a product of sodium hydroxide and benzoic acid (C6H5COOH) (ka = 6.3*10^-5). What is the pH of 0.12 M Sodium benzoate? Please enter significant figures. (Sample problem 18.12 and follow-up problems) QUESTION 6 Determine whether the following salts are acidic, basic, or neutral: NH4Cl (Basic), Sr(NO3)2 (Neutral), KNO2 (Acidic) QUESTION 7 Determine whether solutions of the following salts are acidic, basic, or neutral at 25\u00c2\u00b0C: Cu(CH3COO)2 (Acidic), NH4F (Neutral), KHC6H6O6 (Basic<\/p>\n\n\n\n

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

Question 6: pH of 0.12 M Sodium Benzoate<\/strong><\/h3>\n\n\n\n

Given:<\/strong><\/p>\n\n\n\n

    \n
  • Sodium benzoate (C\u2086H\u2085COONa) is the salt of benzoic acid (C\u2086H\u2085COOH, a weak acid) and sodium hydroxide (NaOH, a strong base).<\/li>\n\n\n\n
  • Ka of benzoic acid = 6.3 \u00d7 10\u207b\u2075<\/li>\n\n\n\n
  • Molarity of sodium benzoate = 0.12 M<\/li>\n<\/ul>\n\n\n\n

    Step 1: Identify the type of salt<\/strong>
    Sodium benzoate is a basic salt<\/strong>, because it is formed from the neutralization of a weak acid (benzoic acid) with a strong base (NaOH).<\/p>\n\n\n\n

    Step 2: Use the Ka of benzoic acid to calculate Kb of benzoate ion<\/strong> Kb=KwKa=1.0\u00d710\u2212146.3\u00d710\u22125=1.59\u00d710\u221210K_b = \\frac{K_w}{K_a} = \\frac{1.0 \\times 10^{-14}}{6.3 \\times 10^{-5}} = 1.59 \\times 10^{-10}Kb\u200b=Ka\u200bKw\u200b\u200b=6.3\u00d710\u221251.0\u00d710\u221214\u200b=1.59\u00d710\u221210<\/p>\n\n\n\n

    Step 3: Set up the ICE table for hydrolysis<\/strong><\/p>\n\n\n\n

    Let the hydrolysis reaction of the benzoate ion (C\u2086H\u2085COO\u207b) be: C6H5COO\u2212+H2O\u21ccC6H5COOH+OH\u2212C_6H_5COO^- + H_2O \\rightleftharpoons C_6H_5COOH + OH^-C6\u200bH5\u200bCOO\u2212+H2\u200bO\u21ccC6\u200bH5\u200bCOOH+OH\u2212<\/p>\n\n\n\n

    Initial concentration of C\u2086H\u2085COO\u207b = 0.12 M
    Change in concentration = \u2013x
    Equilibrium [OH\u207b] = x Kb=x20.12=1.59\u00d710\u221210\u21d2x2=1.91\u00d710\u221211\u21d2x=1.91\u00d710\u221211=4.37\u00d710\u22126K_b = \\frac{x^2}{0.12} = 1.59 \\times 10^{-10} \\Rightarrow x^2 = 1.91 \\times 10^{-11} \\Rightarrow x = \\sqrt{1.91 \\times 10^{-11}} = 4.37 \\times 10^{-6}Kb\u200b=0.12×2\u200b=1.59\u00d710\u221210\u21d2x2=1.91\u00d710\u221211\u21d2x=1.91\u00d710\u221211\u200b=4.37\u00d710\u22126<\/p>\n\n\n\n

    Step 4: Calculate pOH and pH<\/strong> pOH=\u2212log\u2061(4.37\u00d710\u22126)=5.36\u21d2pH=14\u22125.36=8.64\\text{pOH} = -\\log(4.37 \\times 10^{-6}) = 5.36 \\Rightarrow \\text{pH} = 14 – 5.36 = 8.64pOH=\u2212log(4.37\u00d710\u22126)=5.36\u21d2pH=14\u22125.36=8.64<\/p>\n\n\n\n

    Answer (with correct significant figures):<\/strong>
    pH = 8.64<\/strong><\/p>\n\n\n\n

    \n\n\n\n

    Question 6: Classifying Salts as Acidic, Basic, or Neutral<\/strong><\/h3>\n\n\n\n
      \n
    1. NH\u2084Cl<\/strong>: Acidic<\/em>\n
        \n
      • NH\u2084\u207a is a weak acid (conjugate acid of weak base NH\u2083), Cl\u207b is neutral \u2192 Acidic<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Sr(NO\u2083)\u2082<\/strong>: Neutral<\/em>\n
          \n
        • Sr\u00b2\u207a and NO\u2083\u207b come from strong base and strong acid \u2192 Neutral<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • KNO\u2082<\/strong>: Basic<\/em>\n
            \n
          • K\u207a is neutral, NO\u2082\u207b is the conjugate base of a weak acid (HNO\u2082) \u2192 Basic<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

            Corrected Answers:<\/strong><\/p>\n\n\n\n

              \n
            • NH\u2084Cl: Acidic<\/strong><\/li>\n\n\n\n
            • Sr(NO\u2083)\u2082: Neutral<\/strong><\/li>\n\n\n\n
            • KNO\u2082: Basic<\/strong><\/li>\n<\/ul>\n\n\n\n
              \n\n\n\n

              Question 7: Classifying Salts at 25\u00b0C<\/strong><\/h3>\n\n\n\n
                \n
              1. Cu(CH\u2083COO)\u2082<\/strong>: Acidic<\/em>\n
                  \n
                • Cu\u00b2\u207a is a weak Lewis acid, CH\u2083COO\u207b is weakly basic \u2192 overall acidic<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n
                • NH\u2084F<\/strong>: Acidic<\/em>\n
                    \n
                  • NH\u2084\u207a (acidic) and F\u207b (weakly basic), but NH\u2084\u207a dominates \u2192 Acidic<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n
                  • KHC\u2086H\u2086O\u2086<\/strong> (Potassium hydrogen tartrate): Basic<\/em>\n
                      \n
                    • K\u207a is neutral, HC\u2086H\u2086O\u2086\u207b is a weak acid \u2192 salt of weak acid \u2192 Basic<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

                      Corrected Answers:<\/strong><\/p>\n\n\n\n

                        \n
                      • Cu(CH\u2083COO)\u2082: Acidic<\/strong><\/li>\n\n\n\n
                      • NH\u2084F: Acidic<\/strong><\/li>\n\n\n\n
                      • KHC\u2086H\u2086O\u2086: Basic<\/strong><\/li>\n<\/ul>\n\n\n\n
                        \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

                        Sodium benzoate (C6H5COONa) is a product of sodium hydroxide and benzoic acid (C6H5COOH) (ka = 6.3*10^-5). What is the pH of 0.12 M Sodium benzoate? Please enter significant figures. (Sample problem 18.12 and follow-up problems) QUESTION 6 Determine whether the following salts are acidic, basic, or neutral: NH4Cl (Basic), Sr(NO3)2 (Neutral), KNO2 (Acidic) QUESTION 7 […]<\/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-233022","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/233022","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=233022"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/233022\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=233022"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=233022"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=233022"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}