1. The problem statement, all variables and given/known data Just want to check that I've used the correct method for this thermodynamics question i've been set. Any clarification would be greatly appreciated. So I have 0.5kg of gas held in a rigid container of volume 0.25m^3 at a temperature of 20°C. 20kJ of heat energy is required to raise the temperature of the gas to 60°C. When the same mass of gas is heated at a constant pressure, 30kJ of heat energy is required to create the same temperature rise. I need to find: ii) The initial pressure of the gas. iii) The change in volume of the gas when it was heated at constant pressure. I've already calculated the specific heat capacities of the gas at constant pressure and constant volume and believe this is correct: R = (Cp = 1.5kJ/kG K) - (Cv = 0.75kJ/kG K) 2. The attempt at a solution ii) V = 0.25m^3 T1 = 20°C (273 + 20 =293K) T2 = 60°C (273 + 60 = 333K) R = 0.75kJ/kG K Q = 20kJ & 30kJ Initial Pressure: PV = MRT Transposed: P = MRT/V P = 0.5 * (0.75*10^3) * 293/0.25 P = 439500 N/M^-2 iii) PV=MRT Transposed: V = MRT/P V = 0.5 * (0.75*10^3) * 333 / 439500 V = 124875 / 439500 V = 0.28m^3 Alternatively, I believe part iii) can be calculated with Boyle's Law (V1T1=V2T2), especially as the question says 'constant pressure'. This gives an answer of 0.22m^3. Not quite sure which would be the correct method. Thanks for any help in advance!