Calculating the Concentration of SO3 and NO

Oct 13, 2025 by wbrum.org 77 views

For the Chemical Equation: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g), Calculating the Number of Moles of NO2(g) to be Added

The equilibrium constant (Kc) is a crucial concept in chemistry that helps us understand the concentrations of reactants and products at equilibrium. In this article, we will explore how to calculate the number of moles of NO2(g) that must be added to a reaction mixture at a certain temperature, given the equilibrium constant (Kc) of 2.60 for the reaction: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g).

Understanding the Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that represents the ratio of the concentrations of the products to the concentrations of the reactants at equilibrium. Mathematically, it is expressed as:

Kc = [C]c [D]d / [A]a [B]b

where [C], [D], [A], and [B] are the concentrations of the products and reactants, respectively, and a and b are their respective stoichiometric coefficients.

Given Information

The equilibrium constant (Kc) is 2.60.
The reaction is: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g).
We want to calculate the number of moles of NO2(g) that must be added to the reaction mixture.

Calculating the Number of Moles of NO2(g)

To calculate the number of moles of NO2(g) that must be added, we need to first determine the initial concentrations of the reactants and products. Let's assume that the initial concentrations of SO2(g) and NO2(g) are [SO2]i and [NO2]i, respectively.

Since the reaction is at equilibrium, we can write the equilibrium expression as:

Kc = [SO3] [NO] / [SO2] [NO2]

We are given that Kc = 2.60. We can rearrange the equation to solve for [NO2]:

[NO2] = [SO3] [NO] / (Kc [SO2])

However, we don't know the concentrations of SO3 and NO. To solve this problem, we need to make some assumptions.

Assumptions

Let's assume that the initial concentration of SO2(g) is 1 M, and the initial concentration of NO2(g) is x M. We will also assume that the reaction is carried out in a closed system, meaning that the volume of the reaction mixture remains constant.

Calculating the Concentration of SO3 and NO

Since the reaction is at equilibrium, we can write the equilibrium expression as:

Kc = [SO3] [NO] / [SO2] [NO2]

We can rearrange the equation to solve for [SO3] [NO]:

[SO3] [NO] = Kc [SO2] [NO2]

Substituting the values, we get:

[SO3] [NO] = 2.60 (1 M) (x M)

Simplifying the equation, we get:

[SO3] [NO] = 2.60x

Calculating the Number of Moles of NO2(g)

Now that we have the concentration of SO3 and NO, we can calculate the number of moles of NO2(g) that must be added.

Let's assume that the volume of the reaction mixture is V liters. The number of moles of NO2(g) that must be added is given by:

n(NO2) = [NO2] V

Substituting the values, we get:

n(NO2) = x M V

To find the value of x, we need to use the equilibrium expression:

Kc = [SO3] [NO] / [SO2] [NO2]

Substituting the values, we get:

2.60 = (2.60x) / (1 M x)

Simplifying the equation, we get:

x = 1 M

Therefore, the number of moles of NO2(g) that must be added is:

n(NO2) = 1 M V

In this article, we calculated the number of moles of NO2(g) that must be added to a reaction mixture at a certain temperature, given the equilibrium constant (Kc) of 2.60 for the reaction: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g). We made some assumptions about the initial concentrations of the reactants and products, and used the equilibrium expression to solve for the number of moles of NO2(g) that must be added.

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Chang, R. (2010). Chemistry. McGraw-Hill.
Levine, I. N. (2012). Physical chemistry. McGraw-Hill.

This article is for educational purposes only and should not be used as a reference for actual laboratory work.
Q&A: Calculating the Number of Moles of NO2(g) to be Added

In our previous article, we explored how to calculate the number of moles of NO2(g) that must be added to a reaction mixture at a certain temperature, given the equilibrium constant (Kc) of 2.60 for the reaction: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g). In this article, we will answer some frequently asked questions (FAQs) related to this topic.

Q: What is the equilibrium constant (Kc)?

A: The equilibrium constant (Kc) is a numerical value that represents the ratio of the concentrations of the products to the concentrations of the reactants at equilibrium.

Q: How do I calculate the number of moles of NO2(g) that must be added?

A: To calculate the number of moles of NO2(g) that must be added, you need to first determine the initial concentrations of the reactants and products. Then, you can use the equilibrium expression to solve for the number of moles of NO2(g) that must be added.

Q: What assumptions do I need to make to solve this problem?

A: To solve this problem, you need to make some assumptions about the initial concentrations of the reactants and products. For example, you may assume that the initial concentration of SO2(g) is 1 M, and the initial concentration of NO2(g) is x M.

Q: How do I calculate the concentration of SO3 and NO?

A: To calculate the concentration of SO3 and NO, you can use the equilibrium expression:

Kc = [SO3] [NO] / [SO2] [NO2]

You can rearrange this equation to solve for [SO3] [NO].

Q: What is the relationship between the number of moles of NO2(g) and the volume of the reaction mixture?

A: The number of moles of NO2(g) that must be added is directly proportional to the volume of the reaction mixture. If the volume of the reaction mixture is V liters, then the number of moles of NO2(g) that must be added is n(NO2) = x M V.

Q: Can I use this method to calculate the number of moles of NO2(g) that must be added for any reaction?

A: No, this method is specific to the reaction: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g). You need to use a different method to calculate the number of moles of NO2(g) that must be added for a different reaction.

Q: What are some common mistakes to avoid when calculating the number of moles of NO2(g) that must be added?

A: Some common mistakes to avoid when calculating the number of moles of NO2(g) that must be added include:

Not making the correct assumptions about the initial concentrations of the reactants and products.
Not using the correct equilibrium expression.
Not solving for the correct variable (in this case, the number of moles of NO2(g) that must be added).

In this article, we answered some frequently asked questions (FAQs) related to calculating the number of moles of NO2(g) that must be added to a reaction mixture at a certain temperature, given the equilibrium constant (Kc) of 2.60 for the reaction: SO2(g) + NO2(g) ⇌ SO3(g) + NO(g). We hope that this article has been helpful in clarifying any confusion and providing a better understanding of this topic.

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Chang, R. (2010). Chemistry. McGraw-Hill.
Levine, I. N. (2012). Physical chemistry. McGraw-Hill.

This article is for educational purposes only and should not be used as a reference for actual laboratory work.