Lesson: Chapter 7 — Quantification of Elements and Compounds

7.2. Relative molecular mass 2 of 10 Reset answers

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Question 2

What is the relative molecular mass of water (H₂O)? (A_r: H = 1, O = 16)

A 17 B 19 C 18 D 34

The right answer is the one marked above.

18. H₂O = (2 × 1) + 16 = 18.

17 comes from ignoring the subscript 2 and taking 1 + 16. A subscript is the number of times that atom's mass must be counted.

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