Question

If the formation of ammonia, shown below, is exothermic at 25°C, what will be the effect of increasing the system's temperature?
3H$_2$(g) + N$_2$(g) $\leftrightarrow$ 2NH$_3$(g)

• A. The value of $K$ will increase
• B. The value of $K$ will decrease
• C. The equilibrium will shift to the right
• D. The [H$_2$] will decrease

Hint:

For exothermic reactions, increasing temperature shifts equilibrium toward reactants and decreases the value of $K$.

Answer 1

The Correct Option is B

The reaction is exothermic, meaning heat is released when ammonia is formed.
According to Le Chatelier’s Principle, increasing the temperature will favor the endothermic direction (reverse reaction) to absorb the added heat.
This shift reduces the formation of NH$_3$ and increases the reactants' concentrations.
Since equilibrium shifts toward the reactants, the equilibrium constant $K$ (which is $\frac{[NH_3]^2}{[N_2][H_2]^3}$) will decrease.