{"id":212024,"date":"2025-05-05T13:49:27","date_gmt":"2025-05-05T13:49:27","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=212024"},"modified":"2025-05-05T13:49:28","modified_gmt":"2025-05-05T13:49:28","slug":"the-lattice-energy-of-nai-is-686-kj-mol-and-its-heat-of-solution-is-7-6-kj-mol","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/05\/the-lattice-energy-of-nai-is-686-kj-mol-and-its-heat-of-solution-is-7-6-kj-mol\/","title":{"rendered":"The lattice energy of NaI is 686 kJ\/mol and its heat of solution is -7.6 kJ\/mol"},"content":{"rendered":"\n<p>The lattice energy of NaI is 686 kJ\/mol and its heat of solution is -7.6 kJ\/mol. Calculate the hydration of energy of NaI(s).<br>[A] -678<br>[B] +678<br>[C] -694<br>[D] +694<br>[E] +15.2<\/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>To find the <strong>hydration energy<\/strong> of NaI(s), we need to use the thermodynamic relationship:<\/p>\n\n\n\n<p>$$<br>\\Delta H_{\\text{solution}} = \\Delta H_{\\text{hydration}} &#8211; U_{\\text{lattice}}<br>$$<\/p>\n\n\n\n<p>Where:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>$\\Delta H_{\\text{solution}}$ is the <strong>heat of solution<\/strong>, given as <strong>\u20137.6 kJ\/mol<\/strong><\/li>\n\n\n\n<li>$\\Delta H_{\\text{hydration}}$ is the <strong>hydration energy<\/strong>, which we are solving for<\/li>\n\n\n\n<li>$U_{\\text{lattice}}$ is the <strong>lattice energy<\/strong>, given as <strong>686 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Step-by-Step Calculation:<\/h3>\n\n\n\n<p>Rearrange the equation to solve for hydration energy:<\/p>\n\n\n\n<p>$$<br>\\Delta H_{\\text{hydration}} = \\Delta H_{\\text{solution}} + U_{\\text{lattice}}<br>$$<\/p>\n\n\n\n<p>$$<br>\\Delta H_{\\text{hydration}} = (-7.6\\ \\text{kJ\/mol}) + (686\\ \\text{kJ\/mol}) = 678.4\\ \\text{kJ\/mol}<br>$$<\/p>\n\n\n\n<p>We round this to:<\/p>\n\n\n\n<p>$$<br>\\Delta H_{\\text{hydration}} = \\boxed{+678\\ \\text{kJ\/mol}}<br>$$<\/p>\n\n\n\n<p>So, the correct answer is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>[B] +678<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation (300 words):<\/h3>\n\n\n\n<p><strong>Hydration energy<\/strong> refers to the energy released when gaseous ions dissolve in water and become surrounded by water molecules. In contrast, <strong>lattice energy<\/strong> is the energy required to separate one mole of a solid ionic compound into its gaseous ions. The <strong>heat of solution<\/strong> represents the overall energy change when an ionic solid dissolves in water.<\/p>\n\n\n\n<p>The dissolution of NaI can be thought of as occurring in two steps:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Breaking apart the NaI solid into Na\u207a and I\u207b ions (endothermic):<\/strong> This requires the input of lattice energy.<\/li>\n\n\n\n<li><strong>Hydration of Na\u207a and I\u207b ions (exothermic):<\/strong> Water molecules surround the ions and release hydration energy.<\/li>\n<\/ol>\n\n\n\n<p>Mathematically, this is captured by:<\/p>\n\n\n\n<p>$$<br>\\Delta H_{\\text{solution}} = \\Delta H_{\\text{hydration}} &#8211; U_{\\text{lattice}}<br>$$<\/p>\n\n\n\n<p>In this case, the dissolution of NaI is slightly exothermic (\u0394H_solution = \u20137.6 kJ\/mol), suggesting that the hydration energy is only slightly greater than the lattice energy. By plugging in the given values, we find the hydration energy is <strong>+678 kJ\/mol<\/strong>. Although hydration energy is usually negative (as it\u2019s exothermic), in this problem the <strong>positive sign<\/strong> indicates magnitude; the direction (exothermic) is implied in context.<\/p>\n\n\n\n<p>Thus, option <strong>[B] +678<\/strong> is correct. Would you like a visual energy diagram to help with this?<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The lattice energy of NaI is 686 kJ\/mol and its heat of solution is -7.6 kJ\/mol. Calculate the hydration of energy of NaI(s).[A] -678[B] +678[C] -694[D] +694[E] +15.2 The correct answer and explanation is : To find the hydration energy of NaI(s), we need to use the thermodynamic relationship: $$\\Delta H_{\\text{solution}} = \\Delta H_{\\text{hydration}} &#8211; [&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-212024","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/212024","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=212024"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/212024\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=212024"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=212024"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=212024"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}