Question

The passage of electricity through an electrolyte solution is caused by the movement of (a) electrons only, (b) cations only, (c) anions only, (d) both cations and anions.

Short answer

The passage of electricity is caused by the movement of both cations and anions (option d).

Step-by-step solution

Understanding Electrolyte Solutions

In an electrolyte solution, the solute dissociates into ions which are charged particles. These ions are responsible for carrying electric current through the solution.

Identifying Charge Carriers

The electric current in an electrolyte solution is carried by both types of ions: cations (positively charged ions) and anions (negatively charged ions).

Evaluating Each Option

Option (a) is incorrect because electrons do not move through the liquid. Option (b) is incorrect because only cations are mentioned. Option (c) is incorrect because only anions are mentioned. Option (d) is correct because both cations and anions are involved in conducting electricity.

Key concepts

Cations and Anions

In electrolyte solutions, the solute divides into ions which are essential for transporting electricity. These ions are split into two kinds: cations and anions.

• Cations: These are positively charged ions. They form when atoms or molecules lose electrons. Think of them as active participants, moving towards the negative electrode, known as the cathode.
• Anions: In contrast, anions are negatively charged ions. They occur when atoms or molecules gain electrons. Anions move towards the positive electrode, called the anode.

This process of splitting into ions is termed 'dissociation'. Both these ions, cations and anions, together play crucial roles in electricity movement through the solution, ensuring a balanced and efficient flow of electric charge.

Electric Current in Solutions

The ability of an electrolyte solution to conduct electricity is due to the motion of its ions. Unlike in metals, where electrons are the main charge carriers, in solutions charge is carried by ions. When a voltage is applied across the solution, cations and anions begin moving in response to the electric field.

• Direction of Movement: Cations move towards the cathode (negative electrode), while anions move towards the anode (positive electrode).
• Path of Electric Current: This ionic migration creates a bridge allowing electric current to flow through the liquid medium.

Unlike solids, electrolyte solutions offer a flexible pathway for ions, resulting in smooth current flow. It is important to note that only ions participate in conduction, not electrons.

Charge Carriers in Electrolytes

The charge carriers in an electrolyte solution are its ions—both cations and anions. Together, these ions enable the solution to conduct electricity.

• Ionic Charge Carriers: Cations are attracted to the cathode, while anions are drawn towards the anode. This dual movement facilitates the current flow, unlike single-charge systems.
• Balance of Charges: Electrolyte solutions maintain electrical neutrality due to the equal and opposite movement of cations and anions, which balances the overall charge.

This balanced flow is crucial because it ensures that the solution remains stable even during the passage of electricity. In essence, both cations and anions are significant, and omitting either would prevent electric current from flowing effectively in the solution.