For the equilibrium $\mathrm{N_2(g)} + 3\mathrm{H_2(g)} \rightleftharpoons 2\mathrm{NH_3(g)}$, $\Delta H < 0$ (exothermic). If the temperature of the system is INCREASED at constant pressure, the equilibrium constant $K_c$ for the forward reaction

1. For an exothermic reaction, heat is a PRODUCT. Treat heat as a notional product when applying Le Chatelier. 2. Increasing temperature ADDS heat to the system; Le Chatelier says equilibrium shifts to ABSORB the added heat — i.e. in the ENDOTHERMIC (reverse) direction. 3. Shifting toward reactants means [products] decreases and [reactants] increases, so $K_c = [\text{products}]/[\text{reactants}]$ DECREASES. 4. Quantitatively, NCERT Table 6.5 confirms: for ammonia synthesis, $K_p$ drops from $6.8\times 10^5$ at 298 K to $41$ at 400 K to $0.036$ at 500 K — by orders of magnitude. 5. Option A would apply to an ENDOTHERMIC reaction. Option C would be true for a catalyst, not temperature. Option D has no physical basis. _Source: NCERT Class 11 Chemistry, Ch 6, §6.8 (Temperature effect — exothermic $\mathrm{NH_3}$ synthesis), p. 20 + Table 6.5._