Question

Write a balanced equation for the decomposition of water by electrolysis.

Short answer

The balanced equation is: 2H_2O ightarrow 2H_2 + O_2 .

Step-by-step solution

Identify Reactants and Products

Electrolysis of water is a chemical reaction where water is broken down into its basic components. The reactants for this process are water ( 2H_2O ) molecules, which will decompose into products: hydrogen gas ( H_2 ) and oxygen gas ( O_2 ).

Write the Unbalanced Equation

The unbalanced equation for the decomposition of water by electrolysis can be written based on the identified reactants and products: H_2O ightarrow H_2 + O_2 .

Balance Hydrogen Atoms

In water, there are two hydrogen atoms per molecule of water, and in the product hydrogen gas, each molecule also has two hydrogen atoms. To match the number of hydrogen atoms, we balance by adding a coefficient of 2 in front of H_2O : 2H_2O ightarrow 2H_2 + O_2 .

Balance Oxygen Atoms

Now, the equation has 2 oxygen atoms on the reactants side from 2H_2O , and 2 atoms in the products because oxygen gas is O_2 , which is already balanced by having one O_2 molecule for the two water molecules. Therefore, the equation 2H_2O ightarrow 2H_2 + O_2 is balanced.

Verification

Verify the equation by counting atoms on both sides. There are 4 hydrogen atoms and 2 oxygen atoms on both reactant and product sides, confirming it is balanced.

Key concepts

Electrolysis of Water

Electrolysis of water is an intriguing chemical process that involves breaking down water into its basic gaseous components—hydrogen and oxygen. This is achieved by passing an electric current through water, typically in the presence of an electrolyte to enhance the process. During electrolysis, the electric current breaks the chemical bonds in water molecules, leading to the liberation of hydrogen gas at the cathode and oxygen gas at the anode.

The process of electrolysis is fundamental not just in chemistry textbooks but also in real-world applications. It is used in industries for producing hydrogen fuel, which is considered a clean energy source. Understanding this process also helps in grasping the concept of redox reactions, where reduction and oxidation occur simultaneously.

• Reactant: Water ( H_2O )
• Products: Hydrogen ( H_2 ) and Oxygen ( O_2 )
• Energy Source: Electric current

The beauty of electrolysis is its simplicity and efficiency in converting one stable molecule into essential gases involved in many chemical and industrial processes.

Balancing Chemical Equations

Balancing chemical equations is a crucial skill in chemistry that ensures the same number of atoms for each element is present on both sides of the reaction. This follows the law of conservation of mass, which states that matter cannot be created or destroyed during a chemical reaction.

When dealing with the electrolysis of water, it is necessary to write a balanced equation that accurately reflects this breaking down process. Initially, the equation might look like:

Unbalanced equation:

\[H_2O \rightarrow H_2 + O_2\]To balance this, we need to ensure the same number of hydrogen and oxygen atoms appear on each side.

Steps to Balance:

• Count hydrogen atoms: Start by balancing hydrogen, as it appears in both reactants and products. Water has 2 hydrogens per molecule.
• Adjust coefficients: By placing a '2' in front of water and hydrogen gas, we align the number of hydrogen atoms: \[2H_2O \rightarrow 2H_2 + O_2\]
• Check oxygen atoms: Each water molecule contributes one oxygen, already balanced with one \(O_2\) molecule for two molecules of water.

Balancing equations is like a logical puzzle, where you adjust coefficients to reflect the conservation of all atoms involved.

Decomposition Reactions

Decomposition reactions are a class of chemical reactions where one substance breaks down into multiple simpler substances. This type of reaction is often triggered by the addition of energy, such as heat, light, or electricity, as seen in electrolysis.

In the context of water electrolysis, the decomposition reaction involves disrupting the bonds holding the hydrogen and oxygen atoms together. The general format of a decomposition reaction is:

General format:

\[AB \rightarrow A + B\]In our specific example, it's represented as:

• Reactant (H_2O): The compound undergoing decomposition
• Products (H_2, O_2): The resulting simpler substances

Decomposition reactions are vital in various scientific and industrial processes, such as metallurgy, chemical manufacturing, and even the functioning of airbags in vehicles. Recognizing and understanding these reactions are fundamental in predicting the behavior of substances under various conditions.