I am not sure how to solve this:

a stoichiometric mixture of methane and air explodes in a closed module. the specific internal energy liberated by the explosion is 2730kJ/kg. The heat capacity at constant volume of all species before and after the explosion is 1.08 kJ/kg.K and is independent of the temperature. you may assume the mixture behaves ideally.

a. estimate the rise in temperature

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given it's a close system, du = q + w

given it's a closed module, i assume it's a constant volume reactor, hence w = 0

du = q => q = -2730kJ/kg

given q = mc(dT), q/m = c(dT)

2730 = (1.08)dT

dT = 2730/1.08 = 2527.778K

temperature rise = dT = 2530K

b. given initial condition is 1bar, 288K, find the immediate pressure after the reaction

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T1 = 288K, P1 = 1bar

T2 = 288 + dT = 2815.78 = 2820K, P2 =

PV = nRT = mRT/M where m: mass of gas and M: molar mass of gas

given m remains constant throughout the process, but not M. In another words, I can't use P1/T1 = P2/T2 to solve.

Please advise..