Question

Which of the following is not characteristic of the salt bridge? (1) It consists of an clectrolyte. (2) It allows ions to migrate. (3) It prevents the bulk flow of liquids. (4) It influcnces the case of redox reactions in the clcctrochemical cells.

Short answer

Statement (4) is not characteristic of the salt bridge.

Step-by-step solution

- Understanding the Function of a Salt Bridge

Analyze the function and purpose of a salt bridge in an electrochemical cell. A salt bridge consists of an electrolyte, which allows ions to migrate, maintaining the electrical neutrality of the solutions in the half-cells, and it prevents the bulk flow of liquids.

- Evaluate Statement (1)

Statement (1): 'It consists of an electrolyte.' This is correct since a salt bridge is made from a salt solution.

- Evaluate Statement (2)

Statement (2): 'It allows ions to migrate.' This is correct as the primary function of the salt bridge is to allow the movement of ions.

- Evaluate Statement (3)

Statement (3): 'It prevents the bulk flow of liquids.' This statement is accurate because the salt bridge prevents mixing of the liquids from the two half-cells.

- Evaluate Statement (4)

Statement (4): 'It influences the case of redox reactions in the electrochemical cells.' This is incorrect because the salt bridge does not directly influence the speed or ease of the redox reactions but rather maintains electrical neutrality.

- Conclusion

Based on the evaluations, statement (4) is not characteristic of the salt bridge.

Key concepts

Electrochemical Cells

Electrochemical cells are devices that convert chemical energy into electrical energy or vice versa. They consist of two electrodes, typically made from different metals, immersed in electrolyte solutions. These electrodes are connected by an external circuit and a salt bridge.
In a typical electrochemical cell, one electrode undergoes oxidation (loses electrons), whereas the other undergoes reduction (gains electrons). This electron movement generates an electric current, which can be used to power electrical devices.

• One common example is the Daniell cell, where zinc and copper electrodes are used.


• Electrochemical cells are used in batteries, fuel cells, and various types of sensors.

Electrolyte Function

The electrolyte is a crucial component in electrochemical cells. It is a substance that contains free ions and conducts electricity. Electrolytes can be in solid, liquid, or gel form.
In electrochemical cells, the electrolyte facilitates the movement of ions between the two half-cells. This movement of ions is essential for maintaining the charge balance as electrons flow through the external circuit.

• In a salt bridge, the electrolyte typically consists of a solution of salt, like potassium nitrate (KNO₃).


• The electrolyte allows the cell to function by ensuring that each half-cell remains electrically neutral.

Ion Migration

Ion migration refers to the movement of ions from one location to another within the electrolyte solution of an electrochemical cell. This movement is essential for the functioning of the cell.
Positive ions (cations) move towards the cathode (reduction site), while negative ions (anions) move towards the anode (oxidation site). This movement helps to balance the charges that arise from the oxidation and reduction reactions.

• Without ion migration, the build-up of charge would quickly stop the flow of electrons and shut down the electrochemical reactions.


• The salt bridge specifically facilitates this migration of ions, ensuring continuous operation of the cell.

Redox Reactions

Redox reactions, or oxidation-reduction reactions, are chemical reactions in which the oxidation states of atoms are changed. These reactions are fundamental to the function of electrochemical cells.
An oxidation reaction occurs at the anode, where electrons are lost. Conversely, a reduction reaction happens at the cathode, where electrons are gained. Together, these reactions generate an electric current.

• For example, in a Daniell cell, zinc undergoes oxidation: Zn → Zn²⁺ + 2e ^- and copper ions undergo reduction: Cu²⁺ + 2e^- → Cu.


• This flow of electrons through the external circuit is harnessed as electrical energy.

Electrical Neutrality

Maintaining electrical neutrality is vital for the continuous operation of electrochemical cells. As electrons move through the external circuit, ions migrate within the cell to balance the charge.

The salt bridge plays a key role by allowing ions to flow between the two half-cells. This prevents the build-up of excess positive or negative charges, which would otherwise halt the redox reactions.

• In the zinc-copper Daniell cell, positive zinc ions accumulate in the anode half-cell, while positive copper ions are deposited in the cathode half-cell.


• The salt bridge ensures these charges are neutralized, maintaining the conditions needed for a continuous flow of electrons and sustained electrical current.