can someone help me out doing these questions please?

B1: (i) What is meant by the enthalpy (heat) of combustion of a chemical substance. [2 marks] (ii) Write a balanced chemical equation for the combustion of ethene (C2H4). Using Hess' law, calculate its heat of combustion given that the heats of formation (Hf) of C2H4,CO2, H2O and O2 are +52.4,393.5,241.8 and 0kJmol1 respectively. [6 marks] (iii) Using the Hc value calculated above in conjunction with the following information on bond energies: E(CH)=+414kJmol1,E(C=O)=+803kJmol1,E(OO)=+498kJmol1, E(OH)=+463kJmol1, work out a value for the bond energy of the carbon-carbon double bond E(C=C) in ethene (C2H4). [6 marks] (iv) Calculate the mass of ethene which must be combusted in order to heat a 20kg quantity of water from room temperature (25C) to its boiling point. Assume C(H2O)=4.18Jg1K1, Ar(C)=12, and Ar(H)=1. [6 marks]