{"id":205435,"date":"2025-03-24T16:19:53","date_gmt":"2025-03-24T16:19:53","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=205435"},"modified":"2025-03-24T16:19:56","modified_gmt":"2025-03-24T16:19:56","slug":"what-is-the-atomic-mass-of-b-if-19-9-of-all-b-atoms-have-a-mass-of-10-01-amu-and-80-1-have-a-mass-of-11-01-amu-2","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/03\/24\/what-is-the-atomic-mass-of-b-if-19-9-of-all-b-atoms-have-a-mass-of-10-01-amu-and-80-1-have-a-mass-of-11-01-amu-2\/","title":{"rendered":"What is the atomic mass of B if 19.9% of all B atoms have a mass of 10.01 amu and 80.1% have a mass of 11.01 amu"},"content":{"rendered":"\n<p>What is the atomic mass of B if 19.9% of all B atoms have a mass of 10.01 amu and 80.1% have a mass of 11.01 amu?<\/p>\n\n\n\n<p>A) 10.21 amu<\/p>\n\n\n\n<p>B) 10.50 amu<\/p>\n\n\n\n<p>C) 10.63 amu<\/p>\n\n\n\n<p>D) 10.81 amu<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-6-color\"><strong>The correct answer and explanation is :<\/strong><\/mark><\/p>\n\n\n\n<p>The atomic mass of boron (B) is calculated by considering the weighted average of its two naturally occurring isotopes: boron-10 (^10B) and boron-11 (^11B). The atomic mass of an element is not a whole number because it reflects the average mass of all its isotopes, weighted by their relative abundances.<\/p>\n\n\n\n<p><strong>Given Data:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>^10B has a mass of 10.01 atomic mass units (amu) and an abundance of 19.9%.<\/li>\n\n\n\n<li>^11B has a mass of 11.01 amu and an abundance of 80.1%.<\/li>\n<\/ul>\n\n\n\n<p><strong>Calculation:<\/strong><\/p>\n\n\n\n<p>To determine the average atomic mass of boron, we use the formula:<\/p>\n\n\n\n<p>[ \\text{Atomic Mass} = (m_1 \\times f_1) + (m_2 \\times f_2) ]<\/p>\n\n\n\n<p>Where:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>( m_1 ) and ( m_2 ) are the masses of the isotopes.<\/li>\n\n\n\n<li>( f_1 ) and ( f_2 ) are the fractional abundances of the isotopes (expressed as decimals).<\/li>\n<\/ul>\n\n\n\n<p>Applying the given values:<\/p>\n\n\n\n<p>[ \\text{Atomic Mass} = (10.01 \\, \\text{amu} \\times 0.199) + (11.01 \\, \\text{amu} \\times 0.801) ]<\/p>\n\n\n\n<p>Calculating each term:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>( 10.01 \\, \\text{amu} \\times 0.199 = 1.990 \\, \\text{amu} )<\/li>\n\n\n\n<li>( 11.01 \\, \\text{amu} \\times 0.801 = 8.819 \\, \\text{amu} )<\/li>\n<\/ul>\n\n\n\n<p>Summing these contributions:<\/p>\n\n\n\n<p>[ \\text{Atomic Mass} = 1.990 \\, \\text{amu} + 8.819 \\, \\text{amu} = 10.809 \\, \\text{amu} ]<\/p>\n\n\n\n<p>Rounding to two decimal places, the atomic mass of boron is approximately 10.81 amu.<\/p>\n\n\n\n<p><strong>Answer:<\/strong><\/p>\n\n\n\n<p>The correct answer is D) 10.81 amu.<\/p>\n\n\n\n<p><strong>Explanation:<\/strong><\/p>\n\n\n\n<p>The atomic mass of an element is a weighted average that accounts for the masses of its isotopes and their relative abundances. In the case of boron, the more abundant isotope (^11B) has a mass of 11.01 amu, while the less abundant (^10B) has a mass of 10.01 amu. The higher abundance of ^11B pulls the average atomic mass closer to 11 amu, which is reflected in the calculated value of approximately 10.81 amu.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/03\/image-1306.png\" alt=\"\" class=\"wp-image-205443\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>What is the atomic mass of B if 19.9% of all B atoms have a mass of 10.01 amu and 80.1% have a mass of 11.01 amu? A) 10.21 amu B) 10.50 amu C) 10.63 amu D) 10.81 amu The correct answer and explanation is : The atomic mass of boron (B) is calculated by [&hellip;]<\/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-205435","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/205435","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=205435"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/205435\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=205435"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=205435"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=205435"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}