Find the relative formula mass of Ca(OH). (H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56, Cu = 63.5, Zn = 65, Ag = 108)
Answer and explanation
Correct answer: C. 74
- Step 1: Add the relative atomic masses, taking each atom as many times as its subscript shows: 1 × 40 (Ca) + 2 × 16 (O) + 2 × 1 (H).
- Step 2: Total .
Answer
74.
Why not the others: 58: the subscript outside the bracket is applied to the last atom only. 57: the subscripts are ignored. 90: an extra oxygen atom is counted.
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