What is the molar mass (in g/mol) of ? (H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Ca = 40)
Answer and explanation
Correct answer: A. 40
- Step 1: To determine the molar mass of , sum the atomic masses of all constituent atoms in the chemical formula.
- Step 2: Substitute the standard atomic weights: 23 + 16 + 1 = 40\ \text{g/mol}.
- Step 3: The resulting sum yields a molar mass of 40\ \text{g/mol}.
Answer
40.
Why not the others: 80 doubles the stoichiometric molar mass; 38 subtracts 2 mass units by miscounting hydrogen or sodium; 42 adds 2 extra mass units.
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