The equilibrium constant, K_p, for the reaction H₂(g) + I₂(g) ⇄ 2HI(g)
Is 55.2 at 425°C. A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?

Question

Quizplus · Accepted Answer

To determine if the system is at equilibrium, calculate the reaction quotient, $Q_c$, and compare it to the equilibrium constant, $K_c$. For the reaction $H_2(g) + I_2(g) \rightleftharpoons 2HI(g)$, $Q_c = \frac{[HI]^2}{[H_2][I_2]}$. Given: $[HI] = 1.055 \, \text{atm}$, $[H_2] = 0.127 \, \text{atm}$, $[I_2] = 0.134 \, \text{atm}$, and $K_c = 55.2$. Calculating $Q_c$ gives $Q_c = \frac{(1.055)^2}{(0.127)(0.134)} = 61.4$, which is greater than $K_c$. This means the system is not at equilibrium, and the reverse reaction must proceed to decrease $Q_c$ to the value of $K_c$.

The Equilibrium Constant, Kp, for the Reaction H2(g) + I2(g)

The Equilibrium Constant, K_p, for the Reaction H₂(g) + I₂(g)