Table of contents

7. Energy, Rate and Equilibrium

The Equilibrium Constant

Join thousands of students who trust us to help them ace their exams!Watch the first video

Multiple Choice

The equilibrium constant, K, for 2 NO (g) + O₂ (g) ⇌ 2 NO₂ (g) is 6.9 x 10².
What is the [NO] in an equilibrium mixture of gaseous NO, O₂, and NO₂ at 500 K that contains 1.5 x 10 ^–2 M O₂ and 4.3 x 10 ^–3 M NO₂?

4.15 x 10^-4 M

1.34 x 10^-3 M

2.04 x 10^-2 M

1.80 x 10^-6 M

Verified step by step guidance

Start by writing the expression for the equilibrium constant, K, for the given reaction: K = [NO2]^2 / ([NO]^2 * [O2]).

Substitute the given values into the equilibrium expression: K = (4.3 x 10^{-3})^2 / ([NO]^2 * 1.5 x 10^{-2}).

Rearrange the equation to solve for [NO]^2: [NO]^2 = (4.3 x 10^{-3})^2 / (K * 1.5 x 10^{-2}).

Substitute the value of K (6.9 x 10^2) into the equation: [NO]^2 = (4.3 x 10^{-3})^2 / (6.9 x 10^2 * 1.5 x 10^{-2}).

Finally, take the square root of the result to find [NO]: [NO] = sqrt((4.3 x 10^{-3})^2 / (6.9 x 10^2 * 1.5 x 10^{-2})).

Master The Equilibrium Constant Concept 1 with a bite sized video explanation from Jules

Problem sets built by lead tutors

Expert video explanations

The equilibrium constant, K, for 2 NO (g) + O2 (g) ⇌ 2 NO2 (g) is 6.9 x 102. What is the [NO] in an equilibrium mixture of gaseous NO, O2, and NO2 at 500 K that contains 1.5 x 10 –2 M O2 and 4.3 x 10 –3 M NO2?