Question

On passing electrical current through an electrolyte solution, the cations (a) move towards cathode with speed equal to that of anions towards anode (b) move with faster speed than that of anions (c) move with different speed as compared to that of anions (d) move with slower speed than that of anions

Short answer

The correct answer is (c) cations move with different speed as compared to that of anions.

Step-by-step solution

Understanding Electrolysis

During electrolysis, an electrical current is passed through an electrolyte (a conducting liquid). This electric current splits the electrolyte's molecules into ions. Positively charged ions (cations) migrate towards the negatively charged electrode (cathode), while negatively charged ions (anions) migrate towards the positive electrode (anode).

Consider the Speed of Ion Movements

The speed of the ions' movement depends upon their individual ionic mobility, which means the ability of the ion to move in an applied electric field. This ionic mobility is influenced by factors like the size, charge, and shape of the ions. However, there's no rule stating that the cations must move faster or slower than the anions.

Select the Right Option

Considering the principles of electrolysis and the fact that ionic mobility (and therefore speed) can differ between different ions, the right answer is (c) cations move with different speed as compared to that of anions. This means that depending on the specifics of the ions involved, cations may move faster, slower or at an equal pace to anions.

Key concepts

Electrolyte solution

An electrolyte solution is a liquid that conducts electricity by allowing ions to move freely. When an electric current is applied, this solution enables the process of electrolysis. In electrolysis, the molecules in the solution are split into charged particles known as ions. These ions are crucial because they are responsible for carrying electric charge through the solution.

Electrolyte solutions are made up of dissolved salts, acids, or bases in water. When these substances dissolve, they break apart into cations, which are positively charged, and anions, which are negatively charged.

• Cations move towards the cathode, the negatively charged electrode.
• Anions move towards the anode, the positively charged electrode.

This process can be observed in many applications, such as in batteries and electroplating.

Ion mobility

Ion mobility refers to an ion's ability to move through an electrolyte solution when an electric field is applied. This concept is important in understanding the speed at which different ions travel during electrolysis. Several factors affect ion mobility:

• Size: Larger ions typically move slower because they experience more resistance as they navigate through the solution.
• Charge: Ions with higher charge often have greater mobility because they are more strongly affected by the electric field.
• Solvent interactions: The interaction between ions and the solvent can slow down their movement.

Each ion in a solution could have a different mobility, leading to variations in the speed at which cations and anions move towards their respective electrodes. Understanding ion mobility helps predict and control the outcomes of electrolysis processes.

Cations and anions

Cations and anions are the charged particles that play a key role in electrolysis. Cations are positively charged ions, while anions are negatively charged. During electrolysis, these ions are attracted to electrodes of opposite charge, a phenomenon crucial in many chemical and industrial processes.

• Cations: These ions migrate towards the cathode. Examples include sodium (Na⁺) and calcium (Ca²⁺), which dissolve in the solution.
• Anions: These ions move towards the anode and can include ions like chloride (Cl^-) and sulfate (SO₄^2-).

By understanding the behavior of cations and anions, we can better grasp how electrolysis alters compounds and pursue new ways to apply this knowledge in technology. The movement of these ions underlies phenomena from metal extraction to refining and electrochemical synthesis.