Question

Combustion of 25.0 g of a hydrocarbon produces 82.0 g of CO2. What is the empirical formula of the compound?

Answer 1

Given Mass of unknown hydrocarbon- 25.0 g Mass of CO2 82.0 g Empirical formula of unknown compound-? The number of moles of CO2 can be calculated by using following formula. The given mass of substance The number of moles Molar mass 82.0 g Number of moles of CO, - 44.01- mol -1.86 mol The number of moles of C can be calculated by using the number of moles of CO2. Since 1 moles of CO2 is equal to the 1 moles of C, so 1.86 moles of CO2 is equal to the 1.86 moles of C. The mass of C is calculated as shown below Mass Number of molesx Molar mass -1.86 mol x12.01 mol 22.34g Thus, the mass of hydrogen 25.0 22.34 -2.66 g

2.66 g The number of moles of H - 1.0079 mol - 2.64 mol Now, divide the number of moles of C and H by the lesser number of moles 1.86 1.86 Number of C atom 2.64 1.86 Number of H atom- The ratio of atoms is fractional. Thus, multiply both the atoms with 5. Therefore, the empirical formula for the hydrocarbon is CfH7.