Empirical and Molecular Formulas

Front

What is an empirical formula?

Back

An empirical formula represents the simplest whole-number ratio of the elements in a compound.

Front

What is a molecular formula?

Back

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

Front

How do you determine the empirical formula from percent composition?

Back

Convert the percentages to grams, then to moles, and find the simplest whole-number ratio.

Front

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

Back

Na₃PO₄.

Front

What is the molecular formula of glycerol with a molar mass of 92.09 g/mol and percent composition of 39.12% C, 8.75% H, and 51.12% O?

Back

C₃H₈O₃.

Front

Which pair has the same empirical formula: NaCrO₄ and Na₂Cr₂O₇, or C₂H₄O₂ and C₆H₁₂O₆?

Back

C₂H₄O₂ and C₆H₁₂O₆.

Front

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

Back

Multiply the empirical formula by a whole number that makes the molar mass equal to the molecular mass.

Front

What is the molecular formula for K₂SO₄ with a molecular mass of 696 g?

Back

K₈S₄O₁₆.

Front

What is the molecular formula if the empirical formula is CH₂O and the molecular molar mass is 180.18?

Back

C₆H₁₂O₆.

Front

What is percent composition?

Back

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