The heat capacity at constant pressure of hydrogen cyanide is given by the expression Cp[J/(mol ∙°C)] = 35.3 + 0.0291T(°C)

(a) Write an expression for the heat capacity at constant volume for HCN, assuming ideal gas behavior.

(b) Calculate ΔU (J/mol) for the constant-pressure process HCN (v, 25°C. 0.80atm) → HCN (v, 100oC, 0.80 atm)

(c) Calculate ΔU (J/mol) for the constant-volume process HCN (v, 25°C, 50 m3/k mol) → HCN (v, 100°C, 50 m3/k mol)

(d) If the process of part (b) were carried out in such a way that the initial and final pressures were each 0.80 atm but the pressure varied during the heating, the value of ΔH would still be what you calculated assuming a constant pressure. Why is this so?