A compound composed of carbon, hydrogen, and chlorine contains 4.19 x 10²³ hydrogen atoms. If 9.00 g of the compound also contains 55.0% chlorine by mass, what is the empirical formula?

• A. CH₃Cl₂
• B. C₂H₄Cl₂
• C. C₂H₅Cl
• D. C₃H₆Cl

Answer: (C)

Verified step by step guidance

1. Determine the mass of chlorine in the compound using the percentage by mass: Multiply the total mass of the compound (9.00 g) by the percentage of chlorine (55.0%) to find the mass of chlorine.
2. Calculate the mass of the remaining elements (carbon and hydrogen) in the compound: Subtract the mass of chlorine from the total mass of the compound.
3. Use the given number of hydrogen atoms (4.19 x 10^23) to find the moles of hydrogen: Divide the number of hydrogen atoms by Avogadro's number (6.022 x 10^23 atoms/mol) to convert to moles.
4. Assume the remaining mass is carbon and calculate the moles of carbon: Subtract the mass of hydrogen (using the moles of hydrogen and its molar mass) from the remaining mass to find the mass of carbon, then divide by the molar mass of carbon to find moles.
5. Determine the empirical formula: Divide the moles of each element (chlorine, hydrogen, and carbon) by the smallest number of moles to find the simplest whole number ratio, which gives the empirical formula.