1. a. Determine the heat of formation of methane (CH4), given that ∆H°f for CO2 is –394 kJ mol−1, ∆H°f for
H2O(g) is –286 kJ mol−1, and ∆Hcomb for CH4 is –890 kJ mol−1
Consider the reaction KClO4(s) KCl(s) + 2O2(g) .
i. Calculate ∆S° given that S°(KClO4(s)) = 151 J K−1 mol−1, S°(KCl(s)) = 83 J K−1 mol−1, and S°(O2(g)) = 205
J K−1 mol−1.
ii. Calculate the standard free energy change and equilibrium constant for the above reaction at 25°C,
given that ∆H°f (KClO4) = –432 kJ mol−1 and ∆H°f (KCl) = –437 kJ mol−1 .
iii. Comment on whether your calculated value of ∆S° in part (i) above is in accordance with what you
would predict from inspection of the balanced equation.
iv. iv. If the reaction is spontaneous, write the expression for the equilibrium constant.
c. The volume of a sample of ideal gas contracts from 6.6 L to 3.3 L under an applied pressure of 1.7 atm. As the
gas contracts, the system gives off 850 J of heat to the surroundings. Calculate ∆E for this change in state.
