Chemistry

Question Analysis
This question tests the student's ability to determine the empirical formula from the percent composition of a compound.

Key Concept Explanation
To find the empirical formula, convert the percent composition to grams, then to moles, and finally determine the mole ratio of each element.

Step-by-step Solution
1. Assume a 100 g sample: Carbon = 38.7 g, Hydrogen = 9.7 g, Oxygen = 51.6 g.
2. Convert grams to moles: Moles of C = 38.7 g ÷ 12.01 g/mol ≈ 3.222 mol, Moles of H = 9.7 g ÷ 1.008 g/mol ≈ 9.623 mol, Moles of O = 51.6 g ÷ 16.00 g/mol = 3.225 mol.
3. Divide each mole value by the smallest mole value (3.222 mol): C: 3.222 ÷ 3.222 = 1, H: 9.623 ÷ 3.222 ≈ 3, O: 3.225 ÷ 3.222 ≈ 1.
4. Round the ratios to the nearest whole numbers: C: 1, H: 3, O: 1.
5. Therefore, the correct answer is

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