Empirical and Molecular Formula

Front

What is an empirical formula?

Back

An empirical formula represents 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 find the empirical formula, divide the subscripts in the molecular formula by their greatest common divisor.

Front

What is the molecular formula for a compound?

Back

The molecular formula shows the actual number of atoms of each element in a molecule of the compound.

Front

If the empirical formula of a compound is CH and its molar mass is 78 g/mol, what is its molecular formula?

Back

C6H6 (Benzene) because the molar mass of CH is 13 g/mol, and 78 g/mol / 13 g/mol = 6.

Front

What is the percent composition of a compound?

Back

Percent composition is the percentage by mass of each element in a compound.

Front

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

Back

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

Front

What is the significance of the molar mass in determining molecular formulas?

Back

Molar mass helps to convert between grams and moles, and is essential for calculating molecular formulas from empirical formulas.

Front

What is the empirical formula for C4H6?

Back

C2H3.

Front

What is the empirical formula for N2S3?

Back

N2S3 (it is already in simplest form).

Front

Given 40.05g S and 59.95g O, how do you find the empirical formula?

Back

Convert grams to moles, find the simplest ratio, and write the empirical formula as SO3.