A 3.000 gram sample of a hydrate compound containing Co, C_2O_4, and H_2O was combusted to give...


A 3.000-gram sample of a hydrated compound containing Co, C2O4, and H_2O was combusted to give 1.316 g of Co_3O_4. What is the percentage of cobalt in the original sample?

Percent Composition

The composition of a compound can be expressed as a mass percentage. This is typically done if the chemical formula is not known and an elemental analysis has been performed. It can be useful to know the percentage of an element since that can also be used as a starting point in stoichiometric calculations if the molecular formula is unknown.

Answer and Explanation: 1

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The molar mass of cobalt oxide is 240.7972 g/mol. The number of moles of cobalt oxide is

{eq}n = \frac {1.316}{240.7972} = 0.005465 {/eq} mol


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Calculating Percent Composition and Determining Empirical Formulas


Chapter 9 / Lesson 7

What is percent composition? Learn how to find the percent composition of compounds. See how to determine the empirical formula from percent composition.

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