Question

The time required to produce 2F electricity with a current of 2.5 amperes is:
(A) 21.44h
(B) 1200min
(C) 50000s
(D) 1.5h

Answer 1

Hint: To answer this question we must recall the basic equations of current electricity. We should also know that one Faraday is the charge carried by one mole of electrons.

Complete step by step answer:
Firstly, we need to know that electric current is a continuous flow of electric charge moving from one place to another along a pathway; required to make all electrical devices work; measured in amperes or amps (A).
Faraday constant is a unit of measurement used in the study of electrochemical reactions and equal to the amount of electric charge that liberates one gram equivalent of any ion from an electrolytic solution. 
One ampere equals one coulomb of charge passing through a point in space over one second. In other words, one ampere equals one coulomb per second.
We know,
Charge on 1 electron = \[1.6 \times {10^{ - 19}}C\]
Also, 1 mole contains = \[6.023 \times {10^{23}}\]electrons.
Therefore,
Charge on 1 mole of electrons = \[1.6 \times {10^{ - 19}} \times 6.023 \times {10^{23}} = 96500C = 1F\]
We now calculate the charge of 2 Faraday as = 2 X 96500 = 193000C

The mathematical formula relating current and charge is:
\[Q = I \times t\]; where Q= charge and I= current
Substituting this equation with the values we have obtained so far,
\[t = \dfrac{Q}{I} = \dfrac{{193000}}{{2.5}} = 77200\,\sec = 1286\,\min \, = \,21.44\,hour\]
Hence, the correct answer is Option (A) 21.44 hour.

Note: According to Faraday's first law, in a given electrochemical reaction the mass of substance that is deposited or released at the electrode surface is directly proportional to the amount of electricity or charge that passes through it. This law is the basis of electrochemistry.