{"id":521,"date":"2017-08-21T10:01:29","date_gmt":"2017-08-21T10:01:29","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/chemistry\/?page_id=521"},"modified":"2017-09-08T06:01:19","modified_gmt":"2017-09-08T06:01:19","slug":"colligative-properties-and-related-laws","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/chemistry\/colligative-properties-and-related-laws\/","title":{"rendered":"Colligative Properties and Related Laws"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\">\n<p><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/solution-interactions\">\u2b05 Previous\u00a0Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/gas-laws-and-solutions\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/the-development-and-theories-of-acids-and-bases\">Next Lesson \u27a1<\/a><\/p>\n<\/div>\n<p><!-- UPDATE NEXT\/PREVIOUS ABOVE --><\/p>\n<p><!-- CONTENT STARTS HERE --><\/p>\n<h1 id=\"title\">Colligative Properties and Related Laws<\/h1>\n<h4>Objective<\/h4>\n<p>In this lesson we will examine colligative properties and the calculations associated with them.<\/p>\n<h4>Previously we covered&#8230;<\/h4>\n<ul>\n<li>Completing K<sub>sp<\/sub> and precipitation formation problems; We should be familiar with\u00a0equilibrium before beginning this lesson.<\/li>\n<li>Describing the interparticle interactions (ion-ion, ion-dipole, dipole-dipole, hydrogen bonds, and\u00a0London dispersion forces) in solutions<\/li>\n<li>Recognizing the difference between diffusion and osmosis<\/li>\n<li>Using concentrations, amounts of solutions, and K<sub>sp<\/sub> values to predict if precipitates\u00a0will form when solutions are mixed<\/li>\n<\/ul>\n<section>\n<h3>Colligative Properties<\/h3>\n<p>Colligative properties are properties of solutions that depend on the concentration of solute\u00a0particles present. The most common colligative properties examined in chemistry include:<\/p>\n<ul>\n<li><abbr title=\"The number of degrees the freezing point of a substance falls when solute particles are added to it\">Freezing\u00a0point\u00a0depression <\/abbr><\/li>\n<li><abbr title=\"The number of degrees that the boiling point of a substance rises when solute particles are added to it\">Boiling\u00a0point\u00a0elevation <\/abbr><\/li>\n<li>Reduction of <abbr title=\"The pressure exerted by vapors which are in equilibrium with their liquid or solid forms \">vapor\u00a0pressure<\/abbr><\/li>\n<li><abbr title=\"The pressure that must be applied to a more concentrated solution to prevent a solvent from passing through a semipermeable membrane during osmosis \">Osmotic\u00a0pressure<\/abbr><\/li>\n<\/ul>\n<h3>Freezing point depression<\/h3>\n<p>Throwing salt on ice lowers the freezing point of water below its normal freezing point, thus melting\u00a0the ice. The freezing point depression can be calculated using the following formula<\/p>\n<p class=\"center\">\u0394T<sub>f<\/sub> = iK<sub>f<\/sub><em>m<\/em><\/p>\n<p>\u0394T<sub>f<\/sub> is the freezing point depression (freezing point of the solution subtracted by the\u00a0freezing point of the pure solvent),\u00a0i is the van\u2019t Hoff factor (the number of solute particles per mole of solute), K<sub>f<\/sub> is the\u00a0freezing point depression constant (this should be negative) and <em>m<\/em> is the molality.<\/p>\n<h3>Boiling point elevation<\/h3>\n<p>In a similar way, the boiling point of a solvent can be raised above its normal boiling point by\u00a0adding solute particles. Boiling point elevation can be calculated using the following formula:<\/p>\n<p class=\"center\">\u0394T<sub>b<\/sub> = iK<sub>b<\/sub><em>m<\/em><\/p>\n<p>\u0394T<sub>b<\/sub> is the boiling point elevation, i is the van\u2019t Hoff factor (the number of\u00a0solute particles per mole of solute), K<sub>b<\/sub> is the\u00a0boiling point elevation constant and <em>m<\/em> is the molality.<\/p>\n<p>The molar mass of the solute can be calculated from freezing point depression or boiling point\u00a0elevation values and some additional data.<\/p>\n<h3>Raoult\u2019s Law<\/h3>\n<p>When nonvolatile solute particles are added, the vapor pressure of a volatile solvent generally\u00a0decreases proportionally to the concentration. This can be expressed as:<\/p>\n<p><center><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/chemistry\/img\/gaslaw\/s4_009.gif\" width=\"89\" height=\"24\" \/><\/center><\/p>\n<p><em>P<\/em><sub>A<\/sub> is the partial pressure of the solvent\u2019s vapor above a solution,\u00a0<em>X<\/em><sub>A<\/sub> is the <abbr title=\"The ratio of the number of moles of one substance to the total number of moles of substances in a solution or mixture\">mole\u00a0fraction<\/abbr> of the solvent in the solution, and <em>P<\/em>\u00b0<sub>A<\/sub> is the vapor\u00a0pressure of the pure solvent.<\/p>\n<h4>Henry\u2019s Law<\/h4>\n<p>Henry\u2019s Law expresses the directly proportional relationship between the solubility of a gas and its\u00a0pressure. Using the equation:<\/p>\n<p class=\"center\"><em>S<sub>g<\/sub> = kP<sub>g<\/sub><\/em><\/p>\n<p><em>S<sub>g<\/sub> <\/em>is the solubility of the gas, <em>k<\/em> is the proportionality\u00a0constant (Henry\u2019s law constant), and<em> P<sub>g<\/sub> <\/em>is the partial pressure of the gas over\u00a0the solution. The proportionality constant is dependent upon the identities of the solute and\u00a0solvent as well as the temperature<em>. <\/em>Henry\u2019s Law can be used to predict the concentration of\u00a0gases in a mixture.<\/p>\n<\/section>\n<p><!-- CONTENT ENDS HERE --><\/p>\n<p><!-- UPDATE NEXT\/PREVIOUS BELOW --><\/p>\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/solution-interactions\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/gas-laws-and-solutions\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/chemistry\/the-development-and-theories-of-acids-and-bases\">Next Lesson\u00a0\u27a1<\/a><\/div>\n<p><a class=\"backtotop\" href=\"#title\">Back to Top<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u2b05 Previous\u00a0Lesson\u00a0Workshop Index\u00a0Next Lesson \u27a1 Colligative Properties and Related Laws Objective In this lesson we will examine colligative properties and the calculations associated with them. Previously we covered&#8230; Completing Ksp and precipitation formation problems; We should be familiar with\u00a0equilibrium before beginning this lesson. Describing the interparticle interactions (ion-ion, ion-dipole, dipole-dipole, hydrogen bonds, and\u00a0London dispersion forces) [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-521","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/pages\/521","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/comments?post=521"}],"version-history":[{"count":6,"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/pages\/521\/revisions"}],"predecessor-version":[{"id":636,"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/pages\/521\/revisions\/636"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/chemistry\/wp-json\/wp\/v2\/media?parent=521"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}