Consider the reaction:
2 NO( g) + Br2( g)Δ2 NOBr( g) Kp = 28.4 at 298 K
In a reaction mixture at equilibrium, the partial pressure of NO is 125 torr and that of Br2 is 148 torr. What is the partial pressure of NOBr in this mixture?

Verified step by step guidance

1. Identify the balanced chemical equation: \(2 \text{NO}(g) + \text{Br}_2(g) \rightleftharpoons 2 \text{NOBr}(g)\).
2. Write the expression for the equilibrium constant \(K_p\) for the reaction: \(K_p = \frac{(P_{\text{NOBr}})^2}{(P_{\text{NO}})^2 (P_{\text{Br}_2})}\).
3. Substitute the given values into the \(K_p\) expression: \(K_p = 28.4\), \(P_{\text{NO}} = 125\) torr, \(P_{\text{Br}_2} = 148\) torr.
4. Rearrange the equation to solve for \(P_{\text{NOBr}}\): \(P_{\text{NOBr}} = \sqrt{K_p \times (P_{\text{NO}})^2 \times P_{\text{Br}_2}}\).
5. Calculate \(P_{\text{NOBr}}\) using the rearranged equation and the given values.

Key Concepts

Equilibrium Constant (Kp)

The equilibrium constant (Kp) is a numerical value that expresses the ratio of the partial pressures of the products to the reactants at equilibrium for a given reaction at a specific temperature. For the reaction 2 NO(g) + Br2(g) ⇌ 2 NOBr(g), Kp = (P_NOBr^2) / (P_NO^2 * P_Br2). This constant helps predict the direction of the reaction and the concentrations of the species involved.

Partial Pressure

Partial pressure is the pressure exerted by a single component of a gas mixture. It is a crucial concept in gas law calculations and is defined as the pressure that the gas would exert if it occupied the entire volume alone. In this question, the partial pressures of NO and Br2 are given, and the partial pressure of NOBr needs to be calculated using the equilibrium expression.

Stoichiometry of the Reaction

Stoichiometry refers to the quantitative relationship between the reactants and products in a chemical reaction. In this case, the stoichiometry of the reaction indicates that two moles of NO react with one mole of Br2 to produce two moles of NOBr. This relationship is essential for calculating the partial pressure of NOBr based on the given partial pressures of the reactants and the equilibrium constant.