Enough of a monoprotic acid is dissolved in water to produce a 0.0192 M solution. The pH of the resulting solution is 2.53. Calculate the Ka for the acid.<\/p>\n\n\n\n
The correct answer and explanation is :<\/strong><\/mark><\/p>\n\n\n\n To calculate the acid dissociation constant (( K_a )) for the monoprotic acid, we use the given information:<\/p>\n\n\n\n The concentration of hydrogen ions (([H^+])) is found using the pH equation:<\/p>\n\n\n\n [ [ [ A monoprotic acid (( HA )) dissociates as:<\/p>\n\n\n\n [ Since ([H^+]) at equilibrium is ( 2.95 \\times 10^{-3} ) M, we set ( x = 2.95 \\times 10^{-3} ).<\/p>\n\n\n\n [ [ [ [ [ [ The acid dissociation constant (( K_a )) measures the strength of an acid in aqueous solution. A higher ( K_a ) value means a stronger acid, while a lower ( K_a ) value indicates a weaker acid. To determine ( K_a ), we must first calculate the equilibrium concentration of hydrogen ions (([H^+])) using the given pH.<\/p>\n\n\n\n The pH is related to ([H^+]) by the equation:<\/p>\n\n\n\n [ Using ( pH = 2.53 ), we calculate ([H^+] = 2.95 \\times 10^{-3} ) M. Since the acid is monoprotic (( HA )), it dissociates into ( H^+ ) and ( A^- ) in a 1:1 ratio. This means the concentration of ( A^- ) at equilibrium is also ( 2.95 \\times 10^{-3} ) M.<\/p>\n\n\n\n The initial acid concentration is given as 0.0192 M. At equilibrium, the remaining ( HA ) concentration is found by subtracting the amount dissociated:<\/p>\n\n\n\n [ Using the expression for ( K_a ):<\/p>\n\n\n\n [ Substituting values, we find:<\/p>\n\n\n\n [ Thus, the acid has a dissociation constant of ( 5.36 \\times 10^{-4} ), indicating a weak acid.<\/p>\n","protected":false},"excerpt":{"rendered":" Enough of a monoprotic acid is dissolved in water to produce a 0.0192 M solution. The pH of the resulting solution is 2.53. Calculate the Ka for the acid. The correct answer and explanation is : Solution: To calculate the acid dissociation constant (( K_a )) for the monoprotic acid, we use the given information: […]<\/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-202033","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/202033","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=202033"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/202033\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=202033"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=202033"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=202033"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Solution:<\/strong><\/h3>\n\n\n\n
\n
Step 1: Determine ([H^+])<\/strong><\/h4>\n\n\n\n
pH = -\\log [H^+]
]<\/p>\n\n\n\n
[H^+] = 10^{-pH} = 10^{-2.53}
]<\/p>\n\n\n\n
[H^+] = 2.95 \\times 10^{-3} \\text{ M}
]<\/p>\n\n\n\nStep 2: Set up the ICE Table for Dissociation<\/strong><\/h4>\n\n\n\n
HA \\rightleftharpoons H^+ + A^-
]<\/p>\n\n\n\nSpecies<\/th> Initial (M)<\/th> Change (M)<\/th> Equilibrium (M)<\/th><\/tr><\/thead> ( HA )<\/td> 0.0192<\/td> (-x)<\/td> (0.0192 – x)<\/td><\/tr> ( H^+ )<\/td> 0<\/td> (+x)<\/td> (x)<\/td><\/tr> ( A^- )<\/td> 0<\/td> (+x)<\/td> (x)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
[HA]_{eq} = 0.0192 – 2.95 \\times 10^{-3} = 0.01625 \\text{ M}
]<\/p>\n\n\n\nStep 3: Calculate (K_a)<\/strong><\/h4>\n\n\n\n
K_a = \\frac{[H^+][A^-]}{[HA]}
]<\/p>\n\n\n\n
K_a = \\frac{(2.95 \\times 10^{-3})^2}{0.01625}
]<\/p>\n\n\n\n
K_a = \\frac{8.70 \\times 10^{-6}}{0.01625}
]<\/p>\n\n\n\n
K_a = 5.36 \\times 10^{-4}
]<\/p>\n\n\n\nFinal Answer:<\/strong><\/h3>\n\n\n\n
K_a = 5.36 \\times 10^{-4}
]<\/p>\n\n\n\nExplanation (300 Words)<\/strong><\/h3>\n\n\n\n
[H^+] = 10^{-pH}
]<\/p>\n\n\n\n
[HA]_{eq} = 0.0192 – 2.95 \\times 10^{-3} = 0.01625 \\text{ M}
]<\/p>\n\n\n\n
K_a = \\frac{[H^+][A^-]}{[HA]}
]<\/p>\n\n\n\n
K_a = \\frac{(2.95 \\times 10^{-3})^2}{0.01625} = 5.36 \\times 10^{-4}
]<\/p>\n\n\n\n