The Law of Definite Proportions states that elements in a compound are always present in the same proportions by mass. The percent composition is the relative mass of each element in a compound. The mass percent is the mass of an element in a compound expressed as a percentage of the total mass of the compound. For example, a water molecule has a composition of 2 hydrogen atoms and 1 oxygen atom. The mass percent of hydrogen is 11.2% and the mass percent of oxygen is 88.8%. These numbers together make up the percent composition of a water molecule. Thus, for any pure sample of water, it will always have this percent composition. That is, water will be 11.2% hydrogen and 88.8% oxygen.<\/p>\n
Example:<\/strong> If a compound has a total mass of 34.37 g, where 12.94 g is magnesium and 21.43 g is phosphorous, what is the percent composition?<\/p>\n Mass percent of Mg = 12.94g\/34.37g = 37.6%<\/p>\n Mass percent of P = 21.43g\/34.37g = 62.4%<\/p>\n Therefore, the percent composition of this compound is 37.6% magnesium and 62.4% phosphorous.<\/p>\n Example:<\/strong> What is sodium chloride, NaCl’s percentage composition?<\/p>\n Assume a sample size of 1 mole so that the mass of NaCl is 58.44 g (since molar mass is 58.44 g\/mole). This would mean the masses of Na and Cl are 22.99g and 35.45g respectively.<\/p>\n Mass percent of Na = 22.99g\/58.44g = 39.3%<\/p>\n Mass percent of Cl = 35.45g\/58.44g = 60.7%<\/p>\n Therefore, the percent composition of NaCl is 39.3% sodium and 60.7% chloride.<\/p>\n <\/p>\n This article was written for you by Samantha<\/strong>, one of the tutors with SchoolTutoring Academy<\/span>.<\/p>\n","protected":false},"excerpt":{"rendered":" The Law of Definite Proportions states that elements in a compound are always present in the same proportions by mass. The percent composition is the relative mass of each element in a compound. The mass percent is the mass of an element in a compound expressed as a percentage of the total mass of the […]<\/p>\n","protected":false},"author":19,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[5],"tags":[845,847,2391,2432],"class_list":["post-5136","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-how-do-you-calculate-mass-percent","tag-how-do-you-calculate-percent-composition","tag-what-is-mass-percent","tag-what-is-percent-composition"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/posts\/5136","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/comments?post=5136"}],"version-history":[{"count":0,"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/posts\/5136\/revisions"}],"wp:attachment":[{"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/media?parent=5136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/categories?post=5136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/schooltutoring.com\/scholarship\/wp-json\/wp\/v2\/tags?post=5136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Calculating Percent Composition from a Chemical Formula<\/h5>\n