What is the molar concentration of pure liquid water at 25 °C (density = 1.00 g/mL, molar mass = 18.02 g/mol)?
Answer and explanation
Correct answer: B. 55.5 M
One liter of water has a volume of 1,000 mL and a mass of 1,000 g. The number of moles in 1,000 g is n = 1,000 g / 18.02 g/mol ≈ 55.49 mol. Therefore, the molar concentration of pure water is [H2O] ≈ 55.5 M.
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