A compound contains 31.2% calcium, 28.6% sulfur, and 40.2% oxygen by mass. What is the empirical formula of this compound?

• A. CaSO3
• B. CaSO4
• C. CaS2O3
• D. Ca2SO4

Answer: (B)

Verified step by step guidance

1. Convert the given mass percentages of each element to moles by dividing each percentage by the atomic mass of the respective element. Use the atomic masses: Ca = 40.08 g/mol, S = 32.06 g/mol, O = 16.00 g/mol. For example, calculate moles of Ca as \(\frac{31.2}{40.08}\).
2. Calculate the moles of sulfur and oxygen similarly: \(\frac{28.6}{32.06}\) for S and \(\frac{40.2}{16.00}\) for O.
3. Determine the simplest whole number mole ratio by dividing all mole values by the smallest number of moles obtained among Ca, S, and O.
4. If any mole ratio is not close to a whole number, multiply all ratios by the smallest integer that converts them to whole numbers (e.g., 2, 3, or 4) to get the empirical formula subscripts.
5. Write the empirical formula using the whole number mole ratios as subscripts for Ca, S, and O respectively, and compare it to the given options to identify the correct empirical formula.