Lesson: Chapter 16 — Changes of Matter

16.2. Chemical equations 6 of 8 Reset answers

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Question 6

Taking Fe = 56 and O = 16, what is the molar mass of Fe₂O₃?

A 104 g mol⁻¹ B 128 g mol⁻¹ C 160 g mol⁻¹ D 72 g mol⁻¹

The right answer is the one marked above.

160 g mol⁻¹. (2 × 56) + (3 × 16) = 112 + 48 = 160.

72 comes from taking 56 + 16 and ignoring the subscripts. A subscript gives the number of those atoms, so it must be used as a multiplier.

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