{"id":248682,"date":"2025-07-08T16:06:40","date_gmt":"2025-07-08T16:06:40","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=248682"},"modified":"2025-07-08T16:06:42","modified_gmt":"2025-07-08T16:06:42","slug":"the-value-of-ka-for-nitrous-acid-hno2-at-25-%e2%88%98c-is-4-5x10%e2%88%924","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/08\/the-value-of-ka-for-nitrous-acid-hno2-at-25-%e2%88%98c-is-4-5x10%e2%88%924\/","title":{"rendered":"The value of\u00a0Ka\u00a0for nitrous acid (HNO2) at 25\u00a0\u2218C is\u00a04.5\u00d710\u22124."},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong>1<\/a><\/sup><\/p>\n\n\n\n\n\n

Correct Answer:<\/strong> The pK\u2090 of nitrous acid is 3.35.<\/p>\n\n\n\n

Based on the information provided, the acid dissociation constant, or K\u2090, for nitrous acid (HNO\u2082) at 25 \u00b0C is 4.5 \u00d7 10\u207b\u2074. This value is a quantitative measure of the strength of an acid in solution.<\/p>\n\n\n\n

The K\u2090 value arises from the equilibrium expression for the dissociation of a weak acid in water. For nitrous acid, the reaction is:
HNO\u2082(aq) + H\u2082O(l) \u21cc H\u2083O\u207a(aq) + NO\u2082\u207b(aq)<\/p>\n\n\n\n

The small magnitude of the K\u2090 value (4.5 \u00d7 10\u207b\u2074) confirms that nitrous acid is a weak acid. This means that when it is dissolved in water, only a small fraction of the HNO\u2082 molecules donate a proton to form hydronium ions (H\u2083O\u207a) and nitrite ions (NO\u2082\u207b). The equilibrium strongly favors the undissociated acid on the left side of the equation.<\/p>\n\n\n\n

A common and convenient way to express acid strength is by using the pK\u2090, which is the negative base-10 logarithm of the K\u2090 value. The calculation is as follows:
pK\u2090 = -log(K\u2090)
pK\u2090 = -log(4.5 \u00d7 10\u207b\u2074)
pK\u2090 \u2248 3.35<\/p>\n\n\n\n

A lower pK\u2090 value corresponds to a stronger acid. This logarithmic scale makes it easier to compare the relative strengths of different acids.<\/p>\n\n\n\n

Furthermore, we can use the K\u2090 of nitrous acid to find the base dissociation constant (K\u2091) for its conjugate base, the nitrite ion (NO\u2082\u207b). The relationship between K\u2090, K\u2091, and the ion product constant for water (K\u2090, which is 1.0 \u00d7 10\u207b\u00b9\u2074 at 25 \u00b0C) is K\u2090 \u00d7 K\u2091 = K\u2090.
K\u2091 for NO\u2082\u207b = K\u2090 \/ K\u2090 = (1.0 \u00d7 10\u207b\u00b9\u2074) \/ (4.5 \u00d7 10\u207b\u2074) \u2248 2.2 \u00d7 10\u207b\u00b9\u00b9. This small K\u2091 value indicates that nitrite is a weak base, which is expected for the conjugate base of a weak acid.<\/p>\n\n\n\n

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

The Correct Answer and Explanation is:1 Correct Answer: The pK\u2090 of nitrous acid is 3.35. Based on the information provided, the acid dissociation constant, or K\u2090, for nitrous acid (HNO\u2082) at 25 \u00b0C is 4.5 \u00d7 10\u207b\u2074. This value is a quantitative measure of the strength of an acid in solution. The K\u2090 value arises from […]<\/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-248682","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/248682","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=248682"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/248682\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=248682"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=248682"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=248682"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}