N2(g) + 3H2(g) ↔ 2NH3(g) ΔH = -90 kJ In the equation above, the yield of ammonia can be decreased by

In the given equation, the forward reaction is exothermic (ΔH = -90 kJ), which means that the yield of ammonia will be favored at lower temperatures. Therefore, increasing the temperature will decrease the yield of ammonia. Additionally, removing ammonia from the reaction mixture as it is formed will drive the equilibrium towards the product side, increasing the yield of ammonia. On the other hand, increasing the pressure or adding a catalyst will not affect the yield of ammonia. Therefore, the correct answer is "increasing the temperature."