Percent Composition Practice Problems

Front

What is percent composition?

Back

Percent composition 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 the percent composition of an element in a compound?

Back

To calculate the percent composition of an element, use the formula: (mass of element in 1 mole of compound / molar mass of compound) x 100.

Front

What is the molar mass of MgBr2?

Back

The molar mass of MgBr2 is approximately 200.89 g/mol (Mg = 24.31 g/mol, Br = 79.90 g/mol x 2).

Front

What is the percent composition of bromine in MgBr2?

Back

The percent composition of bromine in MgBr2 is 87%.

Front

What is the molar mass of NaOH?

Back

The molar mass of NaOH is approximately 40.00 g/mol (Na = 22.99 g/mol, O = 16.00 g/mol, H = 1.01 g/mol).

Front

What is the percent by mass of oxygen in NaOH?

Back

The percent by mass of oxygen in NaOH is 40%.

Front

How many hydrogen atoms are in (NH4)3PO4?

Back

There are 12 hydrogen atoms in (NH4)3PO4.

Front

What is the molar mass of benzene (C6H6)?

Back

The molar mass of benzene is approximately 78.11 g/mol (C = 12.01 g/mol x 6, H = 1.01 g/mol x 6).

Front

What is the percent composition of carbon in benzene?

Back

The percent composition of carbon in benzene is 92.2%.

Front

What is the percent composition of hydrogen in benzene?

Back

The percent composition of hydrogen in benzene is 7.8%.