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Calculate The Equilibrium Partial Pressures of N O2 and No

Reviewed by Calculator Editorial Team

This guide explains how to calculate the equilibrium partial pressures of nitrogen (N), oxygen (O2), and nitric oxide (NO) in a chemical equilibrium system. The calculator on this page provides a quick way to compute these values using the ideal gas law and equilibrium constants.

Introduction

When a chemical reaction reaches equilibrium, the partial pressures of the reactants and products stabilize. For the reaction between nitrogen and oxygen to form nitric oxide:

N2 + O2 ⇌ 2NO

The equilibrium partial pressures of N2, O2, and NO can be calculated using the ideal gas law and the equilibrium constant (Kp).

Formula

The equilibrium partial pressures can be calculated using the following steps:

  1. Determine the equilibrium constant (Kp) for the reaction.
  2. Use the initial partial pressures of N2 and O2.
  3. Calculate the equilibrium partial pressures using the ideal gas law and stoichiometry.

For the reaction N2 + O2 ⇌ 2NO:

Kp = (PNO)2 / (PN2 × PO2)

At equilibrium:

PN2 = PN2,initial - x

PO2 = PO2,initial - x

PNO = 2x

Where x is the change in partial pressure that establishes equilibrium.

Example Calculation

Suppose we have an initial partial pressure of N2 = 0.8 atm and O2 = 0.6 atm, and the equilibrium constant Kp = 1.2.

Using the calculator on this page, we can find the equilibrium partial pressures:

  • PN2 = 0.4 atm
  • PO2 = 0.2 atm
  • PNO = 0.8 atm

This means at equilibrium, the partial pressure of NO is 0.8 atm, while N2 and O2 have decreased to 0.4 atm and 0.2 atm, respectively.

Interpreting Results

The equilibrium partial pressures show how the system adjusts to reach equilibrium. A higher equilibrium partial pressure of NO indicates that the reaction favors the formation of nitric oxide. The calculator helps visualize these changes using a chart.

FAQ

What is the equilibrium constant Kp?
The equilibrium constant Kp is a measure of the ratio of product to reactant concentrations at equilibrium. For partial pressures, it's expressed in terms of atm.
How do I find Kp for my reaction?
Kp can be found in chemistry reference books, experimental data, or calculated from standard free energies of formation.
What if the initial pressures are different?
Use the calculator with your specific initial pressures to find the equilibrium partial pressures.
Can I use this calculator for other reactions?
This calculator is specifically designed for the N2 + O2 ⇌ 2NO reaction. For other reactions, use a different calculator.
What units are used for partial pressures?
Partial pressures are measured in atmospheres (atm).