Understanding Molar Ratios in Chemical Equations

Oct 13, 2025 by wbrum.org 27 views

Molar Ratios Worksheet: Practice Problems and Solutions

Understanding Molar Ratios in Chemical Equations

Molar ratios are a fundamental concept in chemistry that helps us understand the relationship between the amounts of reactants and products in a chemical reaction. In this article, we will explore the concept of molar ratios and practice solving problems using the given equation: $N_2 + 3H_2 \rightarrow 2NH_3$ . We will also discuss how to write molar ratios for different pairs of substances in the equation.

What are Molar Ratios?

Molar ratios are the ratios of the amounts of reactants and products in a chemical reaction. They are expressed as the number of moles of one substance to the number of moles of another substance. Molar ratios are calculated based on the coefficients of the substances in the balanced chemical equation.

Balancing Chemical Equations

Before we can calculate molar ratios, we need to make sure that the chemical equation is balanced. A balanced equation has the same number of atoms of each element on both the reactant and product sides. The equation $N_2 + 3H_2 \rightarrow 2NH_3$ is already balanced, but let's take a closer look at it:

$N_2 + 3H_2 \rightarrow 2NH_3$

In this equation, 1 mole of nitrogen gas ( $N_2$ ) reacts with 3 moles of hydrogen gas ( $H_2$ ) to produce 2 moles of ammonia ( $NH_3$ ).

Writing Molar Ratios

Now that we have a balanced equation, we can write molar ratios for different pairs of substances. Let's start with the first request: writing the molar ratio for $N_2$ to $H_2$ .

Molar Ratio of $N_2$ to $H_2$

To write the molar ratio of $N_2$ to $H_2$ , we need to look at the coefficients of these substances in the balanced equation. The coefficient of $N_2$ is 1, and the coefficient of $H_2$ is 3. Therefore, the molar ratio of $N_2$ to $H_2$ is:

$N_2 : H_2 = 1 : 3$

This means that for every 1 mole of $N_2$ , 3 moles of $H_2$ are required.

Molar Ratio of $NH_3$ to $H_2$

Now, let's write the molar ratio of $NH_3$ to $H_2$ . To do this, we need to look at the coefficients of these substances in the balanced equation. The coefficient of $NH_3$ is 2, and the coefficient of $H_2$ is 3. Therefore, the molar ratio of $NH_3$ to $H_2$ is:

$NH_3 : H_2 = 2 : 3$

This means that for every 2 moles of $NH_3$ , 3 moles of $H_2$ are required.

Molar Ratio of $N_2$ to $NH_3$

Finally, let's write the molar ratio of $N_2$ to $NH_3$ . To do this, we need to look at the coefficients of these substances in the balanced equation. The coefficient of $N_2$ is 1, and the coefficient of $NH_3$ is 2. Therefore, the molar ratio of $N_2$ to $NH_3$ is:

$N_2 : NH_3 = 1 : 2$

This means that for every 1 mole of $N_2$ , 2 moles of $NH_3$ are produced.

Conclusion

In this article, we have learned how to write molar ratios for different pairs of substances in a chemical equation. We have practiced solving problems using the equation $N_2 + 3H_2 \rightarrow 2NH_3$ and have written molar ratios for $N_2$ to $H_2$ , $NH_3$ to $H_2$ , and $N_2$ to $NH_3$ . Molar ratios are an essential concept in chemistry that helps us understand the relationship between the amounts of reactants and products in a chemical reaction.

Practice Problems

Write the molar ratio of $H_2$ to $NH_3$ using the equation $N_2 + 3H_2 \rightarrow 2NH_3$ .
Write the molar ratio of $N_2$ to $H_2$ using the equation $N_2 + 3H_2 \rightarrow 2NH_3$ .
Write the molar ratio of $NH_3$ to $N_2$ using the equation $N_2 + 3H_2 \rightarrow 2NH_3$ .

Answers

$H_2 : NH_3 = 3 : 2$
$N_2 : H_2 = 1 : 3$
$NH_3 : N_2 = 2 : 1$

Additional Resources

Balancing Chemical Equations: A Step-by-Step Guide
Molar Ratios: A Comprehensive Guide
Chemical Equations: A Beginner's Guide