Molar Mass and Percent Composition

Front

What is Molar Mass?

Back

The molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule.

Front

How do you calculate the percentage composition of an element in a compound?

Back

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

Front

What is the molar mass of water (H2O)?

Back

The molar mass of water is 18 g/mol (2 for H and 16 for O).

Front

What is the mass percentage of an element in a compound?

Back

The mass percentage of an element is the ratio of the mass of that element to the total mass of the compound, multiplied by 100.

Front

Calculate the mass of 5.55 moles of carbon monoxide (CO).

Back

Mass = moles x molar mass = 5.55 moles x 28 g/mol = 155 g.

Front

What is the percent by mass of sodium in NaCl?

Back

Percent by mass of sodium in NaCl = (mass of Na / mass of NaCl) x 100% = (23 g / 58.5 g) x 100% = 39%.

Front

What is the atomic mass of Carbon (C)?

Back

The atomic mass of Carbon is approximately 12.01 g/mol.

Front

What is the atomic mass of Oxygen (O)?

Back

The atomic mass of Oxygen is approximately 16.00 g/mol.

Front

How do you find the molar mass of a compound?

Back

To find the molar mass, add the atomic masses of all the atoms in the compound's formula.

Front

What is the mass percentage of Carbon in Carbon dioxide (CO2)?

Back

Mass percentage of Carbon in CO2 = (mass of C / mass of CO2) x 100% = (12 g / 44 g) x 100% = 27.27%.