### Video Transcript

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

In this question, we need to
determine the correct πΎ π expression for the reversible decomposition of
nitrosyl bromide into nitrogen monoxide and diatomic bromine. πΎ 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, letβs 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 πΎ 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 πΎ 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 πΎ π of the given reaction is answer choice (D). πΎ π equals π NO squared times
π Br2 divided by π NOBr squared.