Calculate Delta H degree for the decomposition of C_2(NO_2)_6 according to the e

Question

Calculate Delta H degree for the decomposition of C_2(NO_2)_6 according to the equation C_2(NO_2)_6 (s) rightarrow 2NO_2 (g) + 4NO(g) + 2CO_2 (g) Delta H degree = kJ Suppose 1.26 g of C_2(NO_2)_6 (s) is placed in a 200.0 cm^3 vessel where it is detonated. The heat capacities, C_v, at 25 degree C for the gases formed are as follows: CO_2: 28.5 J mol^-1 K^-1 NO: 21.5 J mol^-1 K^-1 NO_2: 29.5 J mol^-1 K^-1 Assuming the heat capacities don't change and all the heat liberated in the reaction remains in the container, what will be the pressure of the mixture of gases after detonation? P = atm

Explanation / Answer

(a) dHo = dHo(products) - dHo(reactants)

             = (2 x 33.18 + 4 x 90.25 + 2 x -393.51) - (96)

             = -455.66 kJ

(b) Using,

PV = nCv

So the pressure P at volume 0.2 L of the system would be,

P = [(1.26/300) x (2 x 29.5 + 4 x 21.5 + 2 x 28.5)]/0.2 = 4.242 atm

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