# Question Video: Identifying the Expression for πΎ_π for the Decomposition of Nitrosyl Bromide Chemistry

Choose the correct expression for the πΎ_π of the following reaction: 2 NOBr (g) β 2 NO (g) +Brβ (g).

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### Video Transcript

Choose the correct expression for the πΎ π of the following reaction. Two NOBr gas is in equilibrium with two NO gas plus Br2 gas. (A) πΎ π equals π NOBr squared divided by π NO squared times π Br2. (B) πΎ π equals π NO times π Br2 divided by π NOBr. (C) πΎ π equals π NOBr divided by π NO times π Br2. (D) πΎ π equals π NO squared times π Br2 divided by π NOBr squared. (E) πΎ π equals π NO squared times π Br2.

In this question, we need to determine the correct πΎ π expression for the reversible decomposition of nitrosyl bromide into nitrogen monoxide and diatomic bromine. πΎ π is the equilibrium constant for partial pressures. The equilibrium constant for partial pressures is the ratio between the partial pressures of the products and reactants at equilibrium.

To understand how to write an expression for this equilibrium constant, letβs take a look at a generic equilibrium reaction equation. In this equation, the lowercase letters represent stoichiometric coefficients and the uppercase letters represent chemical formulas. To write an expression for πΎ π for this reaction, we start by writing the partial pressures of the products, C and D, in the numerator and the partial pressures of the reactants, A and B, in the denominator. Then, we raise each individual partial pressure to the power of its respective stoichiometric coefficient.

We can follow along with the generic equation to write an expression for the πΎ π of the given reaction. We start by writing the partial pressures of the products, nitrogen monoxide and diatomic bromine, in the numerator and the partial pressure of the reactant, nitrosyl bromide, in the denominator. Then, we raise each partial pressure to the power of the corresponding stoichiometric coefficient.

We can see that the expression that we have written matches the expression shown in answer choice (D). So, the correct expression for the πΎ π of the given reaction is answer choice (D). πΎ π equals π NO squared times π Br2 divided by π NOBr squared.