What is Electrolysis of Water?

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Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

Electrolysis of water is a process that uses electricity to break down water (H2O) into its basic elements: hydrogen gas (H2) and oxygen gas (O2). It's like using an electric current to 'unmix' water into its components.

Simple Example

Quick Example

Imagine you have a bottle of 'mixed fruit juice' (water) and you want to separate it into individual fruits (hydrogen and oxygen). Electrolysis is like using a special electric juicer that only separates the juice into pure 'apple juice' and 'orange juice' using electricity, instead of a normal juicer that just blends them more.

Worked Example

Step-by-Step

Let's say we want to produce hydrogen and oxygen from 36 grams of water.

1. **Understand the reaction:** Water (H2O) breaks down into Hydrogen (H2) and Oxygen (O2).
2. **Write the balanced chemical equation:** 2H2O(l) → 2H2(g) + O2(g)
3. **Calculate molar mass of water:** H = 1 g/mol, O = 16 g/mol. So, H2O = (2 * 1) + 16 = 18 g/mol.
4. **Determine moles of water:** Moles = Mass / Molar Mass = 36 g / 18 g/mol = 2 moles of H2O.
5. **Use stoichiometry:** From the balanced equation, 2 moles of H2O produce 2 moles of H2 and 1 mole of O2.
6. **Calculate mass of products:**
* Mass of H2 = Moles * Molar Mass = 2 moles * (2 * 1 g/mol) = 4 grams of H2.
* Mass of O2 = Moles * Molar Mass = 1 mole * (2 * 16 g/mol) = 32 grams of O2.

ANSWER: 36 grams of water will produce 4 grams of hydrogen gas and 32 grams of oxygen gas.

Why It Matters

Electrolysis of water is key to producing clean hydrogen fuel, which can power rockets for space technology or fuel future cars, helping us reduce pollution. Engineers use this process to design systems for energy storage and even create oxygen for astronauts in space stations.

Common Mistakes

MISTAKE: Thinking that hydrogen and oxygen are produced in equal volumes during electrolysis. | CORRECTION: Hydrogen gas is produced at the cathode (negative electrode) and oxygen gas at the anode (positive electrode), but the volume of hydrogen produced is twice the volume of oxygen, as seen in the balanced chemical equation (2H2O -> 2H2 + O2).

MISTAKE: Believing pure water conducts electricity well enough for efficient electrolysis. | CORRECTION: Pure water is a very poor conductor of electricity. A small amount of an acid (like sulfuric acid) or a base (like NaOH) is usually added to make the water conductive and speed up the process.

MISTAKE: Confusing the electrodes – which one produces hydrogen and which produces oxygen. | CORRECTION: Hydrogen ions (H+) are attracted to the negative electrode (cathode), where they gain electrons to form hydrogen gas. Oxygen ions (O2-) or hydroxide ions (OH-) are attracted to the positive electrode (anode), where they lose electrons to form oxygen gas.

Practice Questions

Try It Yourself

QUESTION: What type of energy is used to break down water during electrolysis? | ANSWER: Electrical energy.

QUESTION: If 10 mL of oxygen gas is collected at the anode during water electrolysis, what volume of hydrogen gas would be collected at the cathode under the same conditions? | ANSWER: 20 mL (since hydrogen volume is twice that of oxygen).

QUESTION: Why is a small amount of an electrolyte (like an acid) added to water before electrolysis? Explain in one sentence. | ANSWER: An electrolyte is added to increase the electrical conductivity of water, making the electrolysis process more efficient.

MCQ

Quick Quiz

Which of the following is NOT a product of the electrolysis of water?

Hydrogen gas

Oxygen gas

Water vapor

None of the above

The Correct Answer Is:

Electrolysis breaks water (H2O) into hydrogen gas (H2) and oxygen gas (O2). Water vapor is simply gaseous water, not a product of its decomposition.

Real World Connection

In the Real World

In India, ISRO (Indian Space Research Organisation) uses hydrogen as a rocket fuel, and electrolysis is a method to produce this clean fuel. Also, companies are exploring using electrolysis to create green hydrogen for buses and trucks, helping to reduce air pollution in our cities, much like how electric auto-rickshaws are becoming popular.

Key Vocabulary

Key Terms

ELECTROLYSIS: The process of using electrical energy to drive a non-spontaneous chemical reaction, like breaking down water | ELECTROLYTE: A substance that produces an electrically conducting solution when dissolved in a polar solvent, like water | CATHODE: The negative electrode where reduction occurs (hydrogen gas is formed) | ANODE: The positive electrode where oxidation occurs (oxygen gas is formed) | HYDROGEN FUEL: Hydrogen gas used as a clean energy source.

What's Next

What to Learn Next

Now that you understand how water is broken down, you can explore 'Fuel Cells'. Fuel cells are like the reverse of electrolysis, where hydrogen and oxygen are combined to produce electricity and water, showing how these concepts are linked in a cycle of energy.