Percent Composition by Mass

Front

What is percent composition by mass?

Back

Percent composition by mass is the percentage by mass of each element in a compound, calculated by dividing the mass of the element by the total mass of the compound and multiplying by 100.

Front

How do you calculate percent composition by mass?

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Percent composition by mass = (mass of element in 1 mole of compound / molar mass of compound) x 100.

Front

What is the percent composition of an element in a compound with a molar mass of 100 g/mol if the mass of the element is 25 g?

Back

Percent composition = (25 g / 100 g/mol) x 100 = 25%.

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If a compound contains 40 g of element A and 60 g of element B, what is the percent composition of element A?

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Percent composition of A = (40 g / (40 g + 60 g)) x 100 = 40%.

Front

What is the percent composition of water (H2O)?

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Molar mass of H2O = 2(1) + 16 = 18 g/mol. Percent composition of H = (2/18) x 100 = 11.11%, O = (16/18) x 100 = 88.89%.

Front

Which choice is the formula for calculating percent by mass?

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Percent by mass = (mass of solute / mass of solution) x 100.

Front

What is the percent composition of carbon in glucose (C6H12O6)?

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Molar mass of C6H12O6 = 6(12) + 12(1) + 6(16) = 180 g/mol. Percent composition of C = (6(12)/180) x 100 = 40%.

Front

If a compound has a total mass of 200 g and contains 50 g of element X, what is the percent composition of element X?

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Percent composition of X = (50 g / 200 g) x 100 = 25%.

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What is the significance of knowing the percent composition by mass of a compound?

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Knowing the percent composition helps in understanding the chemical makeup of a substance, which is essential for stoichiometry and chemical reactions.

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How does percent composition relate to empirical and molecular formulas?

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Percent composition can be used to determine the empirical formula of a compound, which can then be used to find the molecular formula if the molar mass is known.