Empirical and Molecular Formula Practice

Chemistry practice with 20 problems: ten ask for an empirical formula from percentage or mass composition, and ten ask for a molecular formula from a molar mass and either an empirical formula or percentage composition.
File type
Microsoft Word

Updated Oct 19, 2026

Subject
Chemistry, Science
Topic
Empirical Formula, Molecular Formula
Resource types
Activities

From the author

About this resource

This resource includes 20 problems to practise empirical and molecular formula calculations.

The answers and solutions are included, though the document can be edited to meet your lesson's needs.

In the classroom

Teaching tips & learning objectives

Learning objectives

  • Calculate an empirical formula from percentage or mass composition

  • Determine a molecular formula from a molar mass and an empirical formula or percentage composition

Teaching tips

  • Students need atomic masses from a periodic table to work the mole-ratio and molar-mass steps.

Skills covered

  • Mole ratios — converting composition data to the simplest whole-number ratio

  • Molar mass reasoning — scaling an empirical formula up to the molecular formula

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Resource details

Concepts & topics

Core concepts

  • Empirical formula

  • Molecular formula

  • Percentage composition

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