Question

X and y are two hydrocarbons when X is completely burnt in air 0.50 moles of X produce 60 dm ^-3 of co2 and 3 mol of water at RTP . Deduce the molecular formula of x . ( 1 mole of gas at ATP has a volume of 24 dm^3 )

Answer 1

The hydrocarbon X has an empirical formula based on the combustion products of C2.5H6. After adjusting to whole numbers for a molecular formula, X could be pentane with a molecular formula of C5H12.

Step-by-step explanation:

To deduce the molecular formula of hydrocarbon X based on its complete combustion, we can utilize the information given about the volume of CO2 produced and the moles of water produced. There were 0.50 moles of X burned, producing 60 dm3 of CO2 and 3 mol of H2O at RTP. Since 1 mole of a gas occupies 24 dm3 at RTP, we can calculate the number of moles of CO2 produced from the given volume:

60 dm3 CO2 × (1 mol CO2 / 24 dm3) = 2.5 mol CO2

Since the complete combustion of a hydrocarbon produces CO2 and H2O in a molar ratio equal to the number of carbon and hydrogen atoms in the hydrocarbon, respectively, and assuming that each carbon atom in X produces one CO2 molecule, X contains 2.5 moles of carbon (since 2.5 moles of CO2 were produced). Similarly, each mole of X produces 6 moles of hydrogen atoms since each H2O molecule corresponds to two hydrogen atoms. Therefore, X contains 6 moles of hydrogen atoms (as 3 moles of H2O were produced).

So, the empirical formula based on the mole ratio of carbon to hydrogen is C2.5H6. For a molecular formula, these subscripts must be whole numbers, so multiplying by a factor to obtain whole numbers gives us C5H12, which suggests that X could be pentane.