# An inconvenient convention

Chemistry Level 2

Commercial hydrogen peroxide is typically sold with a given percentage of hydrogen peroxide, by weight. This is not very useful in setting up chemical reactions, where we're usually interested in molarity (moles per liter). Suppose you have a preparation of hydrogen peroxide that is 40% hydrogen peroxide by mass (and 60% water). What is its molarity?

Assumptions and Details

• The density of $$\text{H}_2\text{O}_2$$ is 1.45 g/mL.
• The molecular weight of $$\text{H}_2\text{O}_2$$ is 34.0147 g/mole.
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