Determining the Volume of Residual Gases in a Hydrogen and Oxygen Reaction

Understanding the behavior of gases during chemical reactions, particularly when dealing with residual gases, is crucial for a wide range of scientific and industrial applications. This article explains how to determine the volume of residual gases when oxygen gas reacts with hydrogen gas. We'll also explore the importance of Avogadro’s Law in this context.

Introduction to the Reaction between Hydrogen and Oxygen

The reaction between hydrogen and oxygen to form water is a classic example of a combination reaction. The balanced chemical equation for this reaction is:

2H2(g) O2(g) → 2H2O(g)

This equation shows that 2 volumes of hydrogen gas react with 1 volume of oxygen gas to produce 2 volumes of water vapor.

Given Conditions and Calculations

In this scenario, we are given the volume of oxygen gas (40 cm3) and the volume of hydrogen gas (100 cm3) that react together. Let's work through the problem step by step.

Total Volume of Reactants

The total volume of reactants is the sum of the volumes of hydrogen and oxygen gases:

Total volume of reactants 100 cm3 (H2) 40 cm3 (O2) 140 cm3

Volume of Water Produced

According to the balanced equation, the ratio of volumes is 2:1:2 for hydrogen, oxygen, and water vapor, respectively. Therefore, the volume of water vapor produced can be calculated as:

Total volume of products 2 × 40 cm3 (O2) 80 cm3

Volume of Residual Gases

The volume of residual gases is the difference between the total volume of reactants and the total volume of products:

Volume of residual gases 140 cm3 - 80 cm3 60 cm3

Thus, the volume of residual gases after the reaction is 60 cm3.

Application of Avogadro’s Law

In the context of the reaction between hydrogen and oxygen, Avogadro’s Law of combining volumes is significant. Avogadro’s Law states that equal volumes of gases at the same temperature and pressure contain the same number of molecules. This law is useful in determining the volume ratios of gases involved in chemical reactions. In our case, the volume ratio of hydrogen to oxygen is 2:1, which aligns with the balanced equation.

The law is expressed mathematically as:

V1 / n1 V2 / n2

Where V is volume, and n is the number of moles. Using this principle, the calculated 60 cm3 of residual gases can be understood as the volume of unreacted gases after the reaction is complete.

Conclusion

The concept of residual gases in the context of the reaction between hydrogen and oxygen gas is a practical application of stoichiometry and Avogadro’s Law. By understanding these principles, scientists and engineers can better predict and manage the outcomes of various chemical reactions, especially in industries involving hydrogen and oxygen, such as fuel cells and combustion processes.

The key to solving such problems lies in understanding the balanced equation and applying basic principles like Avogadro’s Law. This knowledge can help in optimizing processes, minimizing waste, and ensuring safety in chemical operations.