Question

If a sample of pure hydrogen gas is ignited very carefully, the hydrogen burns gently, combining with the oxygen gas of the air to form water vapor. Write the unbalanced chemical equation for this reaction.

Short answer

The unbalanced chemical equation for the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to form water vapor (H₂O) is: H₂ (g) + O₂ (g) → H₂O (g)

Step-by-step solution

Identify reactants and product

In this reaction, the reactants are hydrogen gas (H₂) and oxygen gas (O₂). The product is water vapor, which has the chemical formula H₂O.

Write the unbalanced chemical equation

Now, we will write the unbalanced chemical equation using the reactants and product identified above: H₂ (g) + O₂ (g) → H₂O (g) This is the unbalanced chemical equation for the reaction between hydrogen gas and oxygen gas to form water vapor.

Key concepts

Hydrogen Combustion

Hydrogen combustion is a chemical reaction where hydrogen gas burns in the presence of oxygen. This process produces water as the main product. The reaction is highly exothermic, meaning it releases a significant amount of energy in the form of heat and sometimes light. This energy release is why hydrogen combustion can be used as a fuel source.
Hydrogen as a gas is quite flammable. When ignited, it combines rapidly with oxygen, typically from the air, resulting in water vapor. This reaction is important not only in chemical studies but also in applications like rocket propulsion and fuel cells.

• Reactants: Hydrogen gas is represented as \(H_2\), and oxygen gas as \(O_2\).
• Product: The primary product formed is water vapor, \(H_2O\).
• Energy: It's crucial to notice that energy released during the reaction can be harnessed for various practical applications.

Understanding hydrogen combustion involves recognizing it as a fundamental reaction that showcases the potential of hydrogen as a clean energy carrier.

Chemical Equations

Chemical equations are symbolic representations of chemical reactions. They provide information about the substances involved in a reaction, showing the reactants converting into products. Representing reactions as equations helps to clearly communicate what occurs during a reaction.
For the hydrogen combustion reaction, the unbalanced chemical equation is written as:

• Reactants: \(H_2 + O_2\)
• Product: \(H_2O\)

This notation tells us that hydrogen and oxygen gases are reacting to form water vapor in gaseous form. Chemical equations need to be written carefully to ensure they accurately depict the nature of the reaction.
In these equations, symbols and notation have specific meanings:

• The plus sign \((+ )\) indicates the combination of reactants in the reaction.
• The arrow \((\rightarrow)\) shows the transformation from reactants to products in the chemical reaction.
• The states of matter involved are denoted as \((g)\) for gases.

Learning how to interpret and write chemical equations is crucial in understanding the changes substances undergo during a chemical reaction.

Balancing Equations

Balancing equations is an essential step in accurately representing a chemical reaction and adhering to the Law of Conservation of Mass. This law states that matter cannot be created or destroyed in a chemical reaction, which means the number of each type of atom must be the same on both sides of the equation.
The unbalanced equation for hydrogen combustion is \(H_2 + O_2 \rightarrow H_2O\), which must be balanced.
Here is a simple step-by-step process to balance this equation:

• Start by counting the number of hydrogen and oxygen atoms on each side. Initially, there are 2 hydrogen atoms and 2 oxygen atoms on the reactant side, with 2 hydrogen and 1 oxygen on the product side.
• Adjust the coefficients to balance the number of each atom. Adding a coefficient of 2 in front of \(H_2O\) yields: \(H_2 + O_2 \rightarrow 2H_2O\).
• Now, you have 2 hydrogen molecules contributing 4 hydrogen atoms and 2 oxygen atoms as reactants. Balance by adding a coefficient of 2 in front of \(H_2\), changing to: \(2H_2 + O_2 \rightarrow 2H_2O\).
• This results in 4 hydrogen atoms on both sides and 2 oxygen atoms, thus balancing the equation.

By balancing the equation, we satisfy the law, ensuring the reaction accurately represents the conservation of matter. Understanding how to balance equations is an important skill for mastering chemistry concepts.