Question

Complete combustion of a 0.0250 mol sample of a hydrocarbon, CxHy, gives 1.680 L of CO2 at STP and 1.351 g of H2O. (a) What is the molecular formula of the hydrocarbon? (b) What is the empirical formula of the hydrocarbon?

Answer 1

The empirical formula of the hydrocarbon is CH and the molecular formula is also CH.

Step-by-step explanation:

First, we need to find the empirical formula of the hydrocarbon. We can do this by converting the given mass of each element into moles. From the given information, we can calculate that there are 1.457 moles of carbon and 1.351 moles of hydrogen. To find the smallest whole number ratio, we divide both values by 1.351, giving us the empirical formula CH.

Next, we can calculate the molar mass of the empirical formula CH, which is 14.03 g. Dividing the given mass of the hydrocarbon (1.351 g) by the molar mass, we find that there are 0.096 mol of the hydrocarbon. To find the molecular formula, we divide the molar mass of the hydrocarbon (1.351 g) by the empirical mass (14.03 g/empirical unit), which gives us 0.096. Therefore, the molecular formula is the same as the empirical formula, CH.