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Electrochemistry question

2018 · 15 Apr · Shift 1 · Q13
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Electrochemistry question

2018 · 15 Apr · Shift 1 · Q13

JEE MainChemistryElectrochemistryMCQ+4 / −1
When an electric currents passed through acidified water, 112 mL of hydrogen gas at N.T.P. was collected at the cathode in 965 seconds. The current passed, in ampere, is :
  1. A
    1.0
  2. B
    0.5
  3. C
    0.1
  4. D
    2.0
View written solutionFree

Correct answer: A

  1. Reaction at the cathode

In electrolysis of acidified water, hydrogen is produced at the cathode:

2H++2e−→H22H^+ + 2e^- \rightarrow H_22H++2e−→H2​

So, 1 mole of H2H_2H2​ requires 2 moles of electrons.

  1. Moles of hydrogen collected

At N.T.P., 111 mole of gas occupies 22.4 L=22400 mL22.4\,\text{L} = 22400\,\text{mL}22.4L=22400mL.

Given volume of hydrogen:

112 mL112\,\text{mL}112mL

Hence,

n(H2)=11222400=1200=0.005 moln(H_2)=\frac{112}{22400}=\frac{1}{200}=0.005\,\text{mol}n(H2​)=22400112​=2001​=0.005mol

  1. Moles of electrons required

From the cathode reaction:

1 mol H2 needs 2 mol e−1\,\text{mol } H_2 \text{ needs } 2\,\text{mol } e^-1mol H2​ needs 2mol e−

Therefore,

n(e−)=2×0.005=0.01 moln(e^-)=2 \times 0.005=0.01\,\text{mol}n(e−)=2×0.005=0.01mol

  1. Total charge passed

Using Faraday constant,

1 mol e−=96500 C1\,\text{mol } e^- = 96500\,\text{C}1mol e−=96500C

So charge passed:

Q=0.01×96500=965 CQ=0.01 \times 96500=965\,\text{C}Q=0.01×96500=965C

  1. Calculate current

Given time:

t=965 st=965\,\text{s}t=965s

Using

I=QtI=\frac{Q}{t}I=tQ​

I=965965=1.0 AI=\frac{965}{965}=1.0\,\text{A}I=965965​=1.0A

  1. Match with options

The correct option is:

A: 1.0 A\boxed{\text{A: }1.0\,\text{A}}A: 1.0A​

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