Find the relative formula mass of Fe(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: A. 107
- Step 1: Add the relative atomic masses, taking each atom as many times as its subscript shows: 1 × 56 (Fe) + 3 × 16 (O) + 3 × 1 (H).
- Step 2: Total .
Answer
107.
Why not the others: 75: the subscript outside the bracket is applied to the last atom only. 73: the subscripts are ignored. 123: an extra oxygen atom is counted.
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