Empirical and Molecular Formulas

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 calculate the empirical formula from mass percentages?

Back

1. Convert mass percentages to grams (assume 100g total). 2. Convert grams to moles using atomic masses. 3. Divide by the smallest number of moles to find the ratio.

Front

What is a molecular formula?

Back

A molecular formula shows the actual number of atoms of each element in a molecule, which can be a multiple of the empirical formula.

Front

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

Back

Divide the molecular molar mass by the empirical formula mass to find the multiplier, then multiply the subscripts in the empirical formula by this number.

Front

Given 40.05% S and 59.95% O, what is the empirical formula?

Back

SO3

Front

What is the empirical formula of a compound with 18.7% Lithium, 16.3% Carbon, and 65.0% Oxygen?

Back

Li2CO3

Front

How do you find the empirical formula from the percentages of elements?

Back

Convert percentages to grams, then to moles, and simplify the mole ratio.

Front

What is the empirical formula for a compound with 42.07% Na, 18.89% P, and 39.04% O?

Back

Na3PO4

Front

What is the empirical formula for a compound with 72.2% Mg and 27.8% N?

Back

Mg3N2

Front

If the empirical formula is CH2O and the molecular molar mass is 180.18, what is the molecular formula?

Back

C6H12O6