For the gaseous reaction , at . If instantaneous partial pressures are , , and , which of the follow — Chemical Equilibrium Chemistry Question
Question
For the gaseous reaction $X(g) + Y(g) \rightleftharpoons Z(g)$, $K_p = 0.5\text{ atm}^{-1}$ at $400\text{ K}$. If instantaneous partial pressures are $P_X = 2\text{ atm}$, $P_Y = 2\text{ atm}$, and $P_Z = 4\text{ atm}$, which of the following is/are correct?
💡 Solution & Explanation
$Q_p = P_Z / (P_X \cdot P_Y) = 4 / (2 \cdot 2) = 1.0\text{ atm}^{-1}$ (A). Since $Q_p (1.0) > K_p (0.5)$, the reaction moves backward (B). Moving backward consumes $Z$, so $P_Z$ decreases (C). The backward reaction produces 2 moles of gas ($X+Y$) for every 1 mole of $Z$ consumed, so the total number of gaseous moles, and hence total pressure, will increase at constant volume (D).