Mole Conversions and Percent Composition

Front

What is the percent composition of a compound?

Back

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

Front

How do you calculate the percent composition of Benzene (C6H6)?

Back

To calculate the percent composition of Benzene, first find the molar mass: C (12.01 g/mol) x 6 + H (1.008 g/mol) x 6 = 78.11 g/mol. Then, %C = (72.06 g / 78.11 g) x 100 = 92.2%, %H = (6.048 g / 78.11 g) x 100 = 7.8%.

Front

What is Avogadro's number?

Back

Avogadro's number is 6.022 x 10^23, which is the number of atoms, ions, or molecules in one mole of a substance.

Front

How many molecules are in 1 mole of a substance?

Back

There are 6.022 x 10^23 molecules in 1 mole of a substance.

Front

How do you convert moles to molecules?

Back

To convert moles to molecules, multiply the number of moles by Avogadro's number (6.022 x 10^23).

Front

How do you calculate the number of moles from grams?

Back

To calculate the number of moles from grams, divide the mass of the substance (in grams) by its molar mass (in g/mol).

Front

What is the molar mass of Calcium Oxide (CaO)?

Back

The molar mass of CaO is calculated as: Ca (40.08 g/mol) + O (16.00 g/mol) = 56.08 g/mol.

Front

How many grams are in 1.6 moles of CaO?

Back

To find grams, multiply moles by molar mass: 1.6 moles x 56.08 g/mol = 90.13 g, rounded to 90 g.

Front

What is the formula to calculate percent composition?

Back

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

Front

How do you find the percent composition of Oxygen in NO2?

Back

Calculate the molar mass of NO2: N (14.01 g/mol) + 2 x O (16.00 g/mol) = 46.01 g/mol. Then, %O = (32.00 g / 46.01 g) x 100 = 69.56%, rounded to 70%.