What is the percentage by mass of Ca in CaCO₃?
Answer and explanation
Correct answer: C. 40%
- Step 1: Mass of Ca in one formula unit = 40; formula mass = 100. Step 2. Percentage = 40 ÷ 100 × 100 = 40%. Answer: 40%. Why not the others: 60% is what you get if you give the percentage of the other element. 28.571% is what you get if you divide by the wrong total. 4% is what you get if you misplace the decimal point.
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