A compound contains 4.07 % hydrogen, 24.27 % carbon and 71.65 % chlorine. Its molar mass is 98.96 g. What are its empirical and molecular formulas?

Step 1: Calculate the moles of each element in the compound.

To do this, we assume that we have 100g of the compound (this makes the percentages equal to grams). Then, we divide the mass of each element by its atomic mass to find the number of moles.

For hydrogen: 4.07g / 1.01g/mol = 4.03 mol

For carbon: 24.27g / 12.01g/mol = 2.02 mol

For chlorine: 71.65g / 35.45g/mol = 2.02 mol

Step 2: Determine the ratio of the elements.

The ratio of H:C:Cl is 4.03:2.02:2.02, which simplifies to 2:1:1.

Step 3: Write the empirical formula.

The empirical formula is C2H2Cl2.

Step 4: Calculate the molar mass of the empirical formula.

The molar mass of C2H2Cl2 is (212.01g) + (21.01g) + (2*35.45g) = 98.94g/mol.

Step 5: Compare the molar mass of the empirical formula to the given molar mass of the compound.

The molar mass of the empirical formula is very close to the given molar mass of the compound (98.94g/mol vs 98.96g/mol), so the empirical and molecular formulas are the same: C2H2Cl2.