Calculate ΔH° for the reaction.

Question

The value of K_c for the reaction below is 0.450 at 50.00°C and 0.660  at 100.00°C.

AB

Calculate ΔH° for the reaction.

Answer 1

Let us consider the van’t Hoff equation:

ln(K2/K1) = -ΔH/R (1/T2 -1/T1)

ln( 0.660/0.450) = -ΔH/8.314 J/Kmol (1/373 - 1/323)

0.383 = -ΔH/8.314(0.00268 - 0.00310)

0.383 = -ΔH/8.314(0.00042)

0.383 = -0.00042ΔH / 8.314

ΔH = 7582 J/mole =7.58 kJ/mole

be sure to check all the math