Consider the equilibrium $\mathrm{N_2(g)} + 3\mathrm{H_2(g)} \rightleftharpoons 2\mathrm{NH_3(g)}$. The value of $K_p$ at $298\,\text{K}$ is $6.8\times 10^5$ (bar$^{-2}$). At this temperature, ammonia synthesis is
Athermodynamically unfavoured (reactants are favoured)
Bthermodynamically favoured (products are favoured)
Cexactly at the midpoint (both sides equally favoured)
Dnot possible because gases cannot reach equilibrium at room temperature
Answer & Solution
Correct answer: B. thermodynamically favoured (products are favoured)
1. NCERT §6.6.1 (Predicting the extent of a reaction): if $K \gg 10^3$, the equilibrium lies STRONGLY to the right (products dominate).
2. Here $K_p = 6.8\times 10^5$, which is much larger than $10^3$. So the equilibrium STRONGLY favours $\mathrm{NH_3}$.
3. In thermodynamic terms, a large $K$ corresponds to a very negative $\Delta G^\circ$ — the products are far more stable than the reactants at this temperature.
4. BUT the reaction is kinetically slow at $298\,\text{K}$, which is why industrial Haber synthesis uses elevated T (lower yield) with a catalyst and high pressure (forces yield back up).
5. Option A reverses the meaning of $K$. Option C would require $K \approx 1$. Option D contradicts the existence of a measurable $K_p$.
_Source: NCERT Class 11 Chemistry, Ch 6, §6.6.1 (Predicting Extent) + Table 6.5 ($K_p$ values for ammonia synthesis), p. 14–15._
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