Lesson: Chapter 7 — Quantification of Elements and Compounds

Working with moles 4 of 10 Reset answers

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Question 4

What amount of water, in moles, is contained in 20 g of it? (Molar mass: H₂O = 18 g mol^-1)

A 2 mol B 1.11 mol C 0.9 mol D 1.8 mol

The right answer is the one marked above.

1.11 mol. n = 20 g ÷ 18 g mol^-1 = 1.11 mol.

0.9 mol comes from inverting the division and taking 18 ÷ 20. The mass is greater than the molar mass, so the answer must be above 1.

Answer the question to continue.