a. State which of the following processes is endothermic and which is exothermic.

(i) The breaking of a chemical bond.

(ii) The forming of a chemical bond.

b. The table below shows the bond energy data for a series of covalent bonds.

(i) Use the information given in the table to calculate the overall enthalpy change for the combustion of ethanol producing carbon dioxide and water.

(ii) Is the process in (i) endothermic or exothermic?

Bond .................. Bond energy/kJ mol−1

C—H ........................................ 435
O=O ........................................ 497
C=O ......................................... 803
H—O ....................................... 464
C—C ........................................ 347
C—O ........................................ 358