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 by mass of an element in a compound?

Back

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

Front

What is the molar mass of KMnO4?

Back

The molar mass of KMnO4 is approximately 158.04 g/mol.

Front

What is the percent by mass of Mn in KMnO4?

Back

35%.

Front

What is the chemical formula for lithium phosphide?

Back

Li3P.

Front

How many lithium atoms are in lithium phosphide?

Back

There are three lithium atoms in lithium phosphide.

Front

What is the total atomic mass of Li3P?

Back

The total atomic mass of Li3P is approximately 23.94 g/mol (Li) + 30.97 g/mol (P) = 53.91 g/mol.

Front

Which element has a greater mass in Li3P, lithium or phosphorus?

Back

Phosphorus.

Front

What is the percent by mass of O in (NH4)3PO4?

Back

43%.

Front

What is the total atomic mass of CO?

Back

The total atomic mass of CO is approximately 12.01 g/mol (C) + 16.00 g/mol (O) = 28.01 g/mol.