Chemical Formulae, Equations and Calculations Part 1
1 mark · EasyState the relative formula mass (Mr) of water, H2O. (Ar: H = 1, O = 16)
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18 (±0)
Common mistakes: Gives answer as 20; Gives answer as 17
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Marking points
B1 · 1 mark · Correctly gives Mr(H2O) as 18.
Worked solution
Mr(H2O) = (2 × 1) + 16 = 2 + 16 = 18.