Question

Calculate the change in internal energy when 2.00 moles of CO are converted to 2.00 moles of CO2 at atmospheric pressure and 25.0 °C:

2CO(g) + O2(g) → 2CO2(g) ∆rHϴ = −566.0 kJ The correct answer is -563.5 kJ, show calculations please.

Answer 1

We know that   H = E + PV = E + nRT , at constant pressure---------------------------------(1)

Here n = Number of gaseous moles of product - number of gaseous moles of reactant

= 2 - 3 = -1

Given temperature T = 25 ^oC = 25 + 293 = 298 K and H = −566.0 kJ.

Here pressure is constant i.e. 1 atmospheric pressure

Putting the values of H, n and T in equation (1), we can write

−566.0 kJ/mole = E + (-1) X 8.314 J/K . mol (1 kJ/1000 J) X 298 K

or, −566.0 kJ/mole = E​ - 2.48 kJ/mole

or, E = −566.0 kJ/mole + 2.48 kJ/mole = -563.52 kJ/mole (Answer)