Question

It is often useful to anticipate, without doing a detailed calculation, whether an increase in temperature will result in a raising or a lowering of a reaction enthalpy. The Cp of a gas of linear molecules is 7/2 R whereas that of a gas of nonlinear molecules if 4R. Decide whether the standard enthalpies of the following reactions will increase or decrease with increasing temperature:

(a) 2 H2(g) + O2(g) -> 2 H2O(g)

(b) N2(g) + 3 H2(g) -> 2 NH3(g)

(c) CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(g)

Answer 1