Question

What is an electrolysis reaction? Give an example of an electrolysis reaction.

Short answer

An electrolysis reaction is a process where an electric current is passed through an electrolyte, resulting in the decomposition of the electrolyte into its constituent elements or ions. This involves the transfer of electrons from the cathode (negative electrode) to the anode (positive electrode). A common example is the electrolysis of water (H₂O), where water decomposes into hydrogen (H₂) and oxygen (O₂) through an electric current. The overall equation for the reaction is \(2H_2O(l) \rightarrow 2H_2(g) + O_2(g)\).

Step-by-step solution

Define an Electrolysis Reaction

An electrolysis reaction is a process in which an electric current is passed through an electrolyte (a substance that conducts electricity), resulting in the decomposition of the electrolyte into its constituent elements or ions. This process involves the transfer of electrons from the cathode (negative electrode) to the anode (positive electrode), driving the chemical reactions at both the electrodes.

Explain the Components of an Electrolysis Reaction

An electrolysis reaction requires the following components: 1. Electrolyte: A substance that conducts electricity, which can be a molten ionic compound or a solution of salts, acids, or alkalis. 2. Cathode: The negative electrode, where reduction occurs (gain of electrons). 3. Anode: The positive electrode, where oxidation occurs (loss of electrons). 4. External power source: A direct current (DC) power source that provides the electric current necessary for the reaction.

Describe the Process of an Electrolysis Reaction

During an electrolysis reaction, the electric current from the external power source is passed through the electrolyte. The positively charged ions (cations) in the electrolyte are attracted to the cathode, where they gain electrons (undergo reduction) to form neutral atoms. Conversely, the negatively charged ions (anions) are attracted to the anode, where they lose electrons (undergo oxidation) and similarly form neutral atoms. The net result is the decomposition of the electrolyte into its constituent elements or ions.

Provide an Example of an Electrolysis Reaction

One common example of an electrolysis reaction is the electrolysis of water (H₂O). In this reaction, water is decomposed into its constituent elements – hydrogen (H₂) and oxygen (O₂) – by passing an electric current through an aqueous solution containing a small amount of an electrolyte (such as a salt or an acid). The balanced chemical equations for the electrolysis of water are: At the cathode (reduction): \(2H_2O(l) + 2e^-\ \rightarrow\ H_2(g) + 2OH^-(aq)\) At the anode (oxidation): \(2H_2O(l) \rightarrow O_2(g) + 4H^+(aq) + 4e^-\) The overall equation for the reaction is: \(2H_2O(l) \rightarrow 2H_2(g) + O_2(g)\) In this example, hydrogen gas is produced at the cathode and oxygen gas at the anode.

Key concepts

Electrolyte

Electrolytes are essential in the process of electrolysis. To understand them, think of them as "conductors" that allow electric currents to flow through a liquid medium. They contain free ions, which move when electricity is supplied. As these ions move, they conduct the electric current required for electrolysis.

Common substances that act as electrolytes include:

• Molten ionic compounds, like molten sodium chloride (table salt).
• Solutions of acids, such as sulfuric acid.
• Alkaline solutions, like solutions of sodium hydroxide.
• Solutions of salts, which are often used in various electrochemical processes.

Electrolytes are crucial as they ensure the movement of ions, enabling the chemical changes necessary for the decomposition of the original compound.

Cathode and Anode

In electrolysis, the cathode and anode play vital roles in the chemical changes that occur.

**Cathode:**
• The cathode is the negative electrode.
• It’s the site where reduction occurs, which means that ions gain electrons.
• For example, in water electrolysis, hydrogen ions gain electrons at the cathode to form hydrogen gas.

**Anode:**
• The anode is the positive electrode.
• It’s the site where oxidation happens, involving the loss of electrons by ions.
• In water electrolysis, oxygen ions lose electrons at the anode to release oxygen gas.
The cathode and anode thus work together, facilitating the separation and collection of different chemical elements from the original compound. They are essential for the progress of the electrochemical reactions during electrolysis.

Water Electrolysis

Water electrolysis is a fascinating process where electricity breaks down water into hydrogen and oxygen gases. It is a prime example of an electrolysis reaction and showcases the practical application of scientific principles.

Here’s how it works:

• An external power source, usually a direct current, is applied to a water solution with an electrolyte added, like a small amount of acid or salt.
• At the **cathode**, water molecules gain electrons and produce hydrogen gas and hydroxide ions. This can be represented by the equation: \(2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)\).
• Meanwhile, at the **anode**, water molecules lose electrons, forming oxygen gas and hydrogen ions. The equation here is: \(2H_2O(l) \rightarrow O_2(g) + 4H^+(aq) + 4e^-\).
• The **overall equation** is a simple net result: \(2H_2O(l) \rightarrow 2H_2(g) + O_2(g)\).

This remarkable process not only demonstrates the breakdown of water but also the principles of conservation of mass and charge. This understanding is critical for fields like energy production, where hydrogen produced through water electrolysis can serve as a clean fuel source.