Question

If a salt bridge is not used between two half cells, what happens to the voltage?
A.Drops to zero
B.Does not change
C.Increases gradually
D.Increases rapidly

Answer 1

Hint: The salt bridge maintains the electrical neutrality of the both half cells and if it is not used, then it would accumulate positive charges on one side and negative charges on the other side. This will ultimately affect the voltage. This much information is quite sufficient to take to the answer.

Complete step by step answer:
In the given question, the role of salt bridge and how it will affect the voltage is asked and this could be answered by knowing the purpose of a salt bridge in an electrochemical cell in which two different half cells are connected.
So, when two different half cells are connected then the salt bridge is inserted between the two cells to connect the two solutions. A salt bridge is basically a U-type tube which connects the oxidation half cell and reduction half cell so it basically acts as a junction.
Salt bridge is used in galvanic cells generally and its main functions are: -
1.To maintain electrical neutrality of the cell
2.Preventing the cell to reach to its equilibrium reaction
3.Act as an electrical contact between the two solutions.
Now when two half cells are connected to each other via a salt bridge, what happens after connecting is electrons start flowing from one solution to another via the external wire connected.
But the salt bridge completes the inner circuit of the electrochemical cell and if no salt bridge is present then what will happen is all the negative ions would get collected towards one half cell and all the positive ions would get collected towards the other half cell.
So ultimately, the reaction would stop occurring and no flow of electrons takes place so voltameter will stop showing any reading which means that Voltage dropped to zero.
The salt bridge does not move electrons but it maintains charge movement and neutrality.

Therefore, the correct option is A i.e. Drops to zero

Note: The salt bridge is generally made of inert and strong electrolyte like \[KCl,{\text{ }}AgN{O_3}\]etc. these are the inert electrolyte which themselves does not take part in the reaction but they just maintain the charge balance along the both sides. Also, each and every substance attached has its own function and they should be known to excel in electrochemistry and answer similar types of questions.