Percent Composition

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 molar mass of a compound?

Back

To calculate the molar mass, sum the atomic masses of all the atoms in the compound's formula, using the periodic table.

Front

What is the formula for calculating percent composition?

Back

Percent Composition = (Mass of Element / Molar Mass of Compound) x 100.

Front

What is the molar mass of magnesium bromide (MgBr2)?

Back

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

Front

What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of magnesium?

Back

13%.

Front

What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of bromine?

Back

87%.

Front

What is the molar mass of sodium hydroxide (NaOH)?

Back

The molar mass of NaOH is 40 g/mol (22.99 g/mol for Na + 15.999 g/mol for O + 1.008 g/mol for H).

Front

What percentage of the total atomic mass of carbon monoxide (CO) is composed of carbon?

Back

43%.

Front

What percentage of the total atomic mass of carbon monoxide (CO) is composed of oxygen?

Back

57%.

Front

If a compound has a molar mass of 58 g/mol and contains 2 grams of oxygen, what is the percent composition of oxygen?

Back

Percent Composition of Oxygen = (2 g / 58 g/mol) x 100 = 3.45%.