Chapter 12, Problem 70E

Ammonia is produced by the Haber process, in which nitrogen and hydrogen are reacted directly using an iron mesh impregnated with oxides as a catalyst. For the reaction

${\text{N}}_2\left(g\right)+3{\text{H}}_2\left(g\right)\rightleftharpoons 2{\text{NH}}_3\left(g\right)$

equilibrium constants (K_p values) as a function of temperature are

300°C, 4.34 × 10⁻³

500°C, 1.45 × 10⁻⁵

600°C, 2.25 × 10⁻⁶

Is the reaction exothermic or endothermic?