Question

When an electric current is passed through acidified water, 112mL of hydrogen gas at N.T.P. was collected at the cathode in 965 seconds. The current passed, in ampere, is _______.
a.) 0.1
b.) 2.0
c.) 1.0
d.) 0.5

Answer 1

Hint: The mass of the substance (m) deposited or liberated at any electrode is directly proportional to the quantity of electricity or charge (Q) passed. Mathematically, it can be written as
$m=Z\times I\times t$
Where, m=mass of the deposited element, I = current passes through it, t=time duration for which current was passed, Z = electrochemical equivalent. So to deposit the same number of moles of a metal will be the same and depends only on the electron involved in the reaction. Or we can say that electricity used is directly proportional to the moles of electrons involved during the deposition reaction.

Complete step by step answer:
Moles of hydrogen = \[\dfrac{112}{22400}=\dfrac{1}{200}=0.005\]
As required charge is directly proportional to the moles of the hydrogen gas,

Charge required will be = $0.005\times 96500=482.5$
Hence we can write
$\Rightarrow I\times t=482.5$
$\Rightarrow I\times 96500=482.5$
$\Rightarrow I=\dfrac{482.5}{96500}$
$\Rightarrow I=0.5\,Ampere$

So, the correct answer is “Option D”.

Note: Michael Faraday reported that the quantity of elements separated by passing an electric current through a molten or dissolved salt is proportional to the quantity of electric charge passed through the circuit. This is known as the basis of the first law of electrolysis. Faraday discovered that when the same amount is passed through different electrolytes or elements which are connected in series, the mass of the substance liberated or deposited at the electrodes in grams is directly proportional to their chemical equivalent or the equivalent weight.