Question

Identification of anode and cathode in an electrochemical cell is made by the use of
(A) galvanometer
(B) salt bridge
(C) voltmeter
(D) potentiometer

Answer 1

Hint: To solve this question we first need to know what is an electrochemical cell. A device that uses the chemical reactions occurring in it to generate electrical energy is known as an electrochemical cell. Electrical energy can also be supplied to an electrochemical cell to enable chemical reactions.

Complete solution:
The anode and cathode in an electrochemical cell can be identified using a voltmeter.
There are two terminals in a voltmeter, positive and negative. The spontaneous direction of the electron flow can be depicted by the sign of the reading on the voltmeter.
The positive value of the voltmeter indicates the direction of the spontaneous flow of electrons from the negative input terminal of the voltmeter (usually black) to the positive input terminal of the voltmeter (usually red).
The negative input terminal of the voltmeter is known as the anode whereas the positive input terminal of the voltmeter is known as the cathode.

Hence the correct option is (C) voltmeter.

Additional Information:
Let us look at the functioning of the devices given in the options.
(A) Galvanometer: Electric current can be measured using a galvanometer which is an electrochemical measuring instrument.
(B) Salt bridge: A device that connects the reduction and oxidation half cells in a galvanic cell (which is a type of electrochemical cell) is known as a salt bridge or ion bridge.
(C) Voltmeter: The voltage or the potential of an electrochemical cell can be measured using a device known as a voltmeter.
(D) Potentiometer: The reference voltage of an electrochemical cell can be measured using a device known as a potentiometer.

Note:
Let us take an example.
In the given cell
\[Zn(s)|Z{{n}^{2+}}(aq)||P{{b}^{2+}}(aq)|Pb(s)\]
When the red wire is connected to the Pb electrode and the black wire is connected to the Zn electrode, a positive value will be shown by the voltmeter.
Hence, we can say that the flow of electrons takes place from the zinc half-cell to the lead half-cell.
Or, we can say that the zinc half-cell is the anode whereas the lead half-cell is the cathode.