Calculate the relative formula mass of calcium hydroxide, Ca(OH)2. (Ca = 40, O = 16, H = 1)
Answer and explanation
Correct answer: B. 74
- Step 1: The OH group is in brackets with 2: 2 x (16 + 1) = 34. Step 2. Mr = 40 + 34 = 74. Answer: 74. Why not the others: 57: That counts only one OH group. 58: That treats the 2 as applying only to the hydrogen. 56: That is the formula mass of calcium oxide.
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