An unknown compound contains only carbon, hydrogen, and chlorine. Using combustion analysis, you burned 22.56 mg of the sample and collected 7.11 mg of H2O and 52.93 mg of CO2. What is the empirical formula of this compound?

• A. CH2Cl
• B. C2H3Cl
• C. C2H4Cl
• D. C3H6Cl2

Answer: (C)

Verified step by step guidance

1. Determine the moles of carbon in the compound by using the mass of CO2 produced. Use the molar mass of CO2 (44.01 g/mol) to convert the mass of CO2 to moles, and then use the stoichiometry of the reaction to find the moles of carbon. Since each mole of CO2 contains one mole of carbon, the moles of carbon are equal to the moles of CO2.
2. Calculate the moles of hydrogen in the compound by using the mass of H2O produced. Use the molar mass of H2O (18.02 g/mol) to convert the mass of H2O to moles, and then use the stoichiometry of the reaction to find the moles of hydrogen. Since each mole of H2O contains two moles of hydrogen, multiply the moles of H2O by 2 to get the moles of hydrogen.
3. Determine the mass of carbon and hydrogen in the original sample using their respective moles and atomic masses (carbon: 12.01 g/mol, hydrogen: 1.008 g/mol). Subtract the combined mass of carbon and hydrogen from the total mass of the sample to find the mass of chlorine.
4. Calculate the moles of chlorine in the compound using the mass of chlorine obtained in the previous step and the atomic mass of chlorine (35.45 g/mol).
5. Determine the empirical formula by finding the simplest whole number ratio of moles of carbon, hydrogen, and chlorine. Divide the moles of each element by the smallest number of moles calculated in the previous steps to obtain the ratio, and use these ratios to write the empirical formula.