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

Front

What is the empirical formula?

Back

The empirical formula is the simplest whole-number ratio of atoms of each element in a compound.

Front

How do you determine the empirical formula from a molecular formula?

Back

To determine the empirical formula, divide the subscripts in the molecular formula by their greatest common divisor.

Front

What is the difference between empirical and molecular formulas?

Back

The empirical formula shows the simplest ratio of elements, while the molecular formula shows the actual number of atoms of each element in a molecule.

Front

What is the gram-formula mass?

Back

The gram-formula mass is the mass of one mole of a compound, calculated by summing the atomic masses of all atoms in the formula.

Front

How do you find 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 percent by mass of fluorine in CaF2?

Back

The percent by mass of fluorine in CaF2 is 49%.

Front

How do you find the empirical formula from percent composition?

Back

Convert the percent composition to grams, then to moles, and divide by the smallest number of moles to find the ratio.

Front

What is the percent composition of Cl in HClO3?

Back

The percent composition of Cl in HClO3 is 42%.