Gce Model Questions Vol1 2017 Chemistry Question 32

A hydrocarbon \(\mathrm{C_xH_y}\) is burnt completely in excess oxygen. From 1.23 g of the hydrocarbon, 2.04 g of \(\mathrm{CO_2}\) and 1.00 g of \(\mathrm{H_2O}\) are obtained. \(\text{(a)}\) Determine the empirical formula of the hydrocarbon. \(\text{(b)}\) The hydrocarbon is known to be an alkane with a molar mass below 100 g·mol⁻¹; give its molecular formula. \(\text{(c)}\) The combustion released 48.5 kJ per gram of the hydrocarbon. Calculate the standard enthalpy of combustion per mole. \(\text{(d)}\) Using the standard enthalpies of formation \(\Delta_fH^\circ(\mathrm{CO_2(g)})=-393.5\ \text{kJ·mol}^{-1}\) and \(\Delta_fH^\circ(\mathrm{H_2O(l)})=-285.8\ \text{kJ·mol}^{-1}\), estimate the standard enthalpy of formation of the hydrocarbon.