Rank the acids in order of increasing pK, 3. (3 marks) Caffeine, the stimulant in coffee and tea, is a weak base that ionizes in water
according to the equation:
CH19N, O2(aq) + H2O(l) – HC H1N, 0+ (aq) + OH- (aq)
A 0.15 M solution of caffeine at 25°C has a pH of 8.45. Determine the Kb of caffeine.

option c: 1605.1 kj

the balanced chemical reaction for combustion of methane is as follows:

here, enthalpy formation of is -74.7 kj/mol, 0 kj/mol, -393.5 kj/mol and -241.82 kj/mol respectively.

the heat released or can be calculated as follow:

putting the values,

thus, heat released by combustion of 1 mol of methane is 802.54 kj/mol. thus, for 2 mol, heat released will be:

therefore, heat released by the combustion of 2 mol of methane is 1605.1 kj.