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JEE Main

Explore popular questions from Redox Reactions for JEE Main. This collection covers Redox Reactions previous year JEE Main questions hand picked by experienced teachers.

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Redox Reactions

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Q 1. Calcium carbonate reacts with aqueous HCl to give {tex} \mathrm { CaCl } _ { 2 } {/tex} and {tex} \mathrm { CO } _ { 2 } {/tex} according to the reaction, {tex} \mathrm { CaCO } _ { 3 } ( \mathrm { s } ) + {/tex} {tex} 2 \mathrm { HCl } ( \mathrm { aq } ) \rightarrow \mathrm { CaCl } _ { 2 } ( \mathrm { aq } ) + \mathrm { CO } _ { 2 } ( \mathrm { g } ) + \mathrm { H } _ { 2 } \mathrm { O } ( \mathrm { l } ) {/tex} The mass of {tex} \mathrm { CaCO } _ { 3 } {/tex} is required to react completely with 25{tex} \mathrm { mL } {/tex} of 0.75{tex} \mathrm { M } \mathrm { HCl } {/tex} is

A

0.1{tex} g {/tex}

B

0.5{tex} g {/tex}

C

1.5{tex} g {/tex}

0.94{tex} g {/tex}

Explanation

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Q 2. How many moles of electron is needed for the reduction of each mole of {tex} \mathrm { Cr } {/tex} in the reaction,
{tex} \mathrm { CrO } _ { 5 } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \longrightarrow \mathrm { Cr } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } + \mathrm { H } _ { 2 } \mathrm { O } + \mathrm { O } _ { 2 } {/tex}

A

4

3

C

5

D

7

Explanation

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Q 3. The incorrect order of decreasing oxidation number of S in compounds is

A

{tex} \mathrm { H } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 7 } > \mathrm { Na } _ { 2 } \mathrm { S } _ { 4 } \mathrm { O } _ { 6 } > \mathrm { Na } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 3 } > \mathrm { S } _ { 8 } {/tex}

B

{tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 5 } > \mathrm { H } _ { 2 } \mathrm { SO } _ { 3 } > \mathrm { SCl } _ { 2 } > \mathrm { H } _ { 2 } \mathrm { S } {/tex}

C

{tex} \mathrm { SO } _ { 3 } > \mathrm { SO } _ { 2 } > \mathrm { H } _ { 2 } \mathrm { S } > \mathrm { S } _ { 8 } {/tex}

{tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } > \mathrm { SO } _ { 2 } > \mathrm { H } _ { 2 } \mathrm { S } > \mathrm { H } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 8 } {/tex}

Explanation



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Q 4. Which reaction does not represent autoredox or disproportionation:

A

{tex} \mathrm { Cl } _ { 2 } + \mathrm { OH } ^ { - } \longrightarrow \mathrm { Cl } ^ { - } + \mathrm { ClO } _ { 3 } ^ { - } + \mathrm { H } _ { 2 } \mathrm { O } {/tex}

B

{tex} 2 \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } \longrightarrow \mathrm { H } _ { 2 } \mathrm { O } + \mathrm { O } _ { 2 } {/tex}

C

{tex} 2 \mathrm { Cu } ^ { + } \longrightarrow \mathrm { Cu } ^ { + 2 } + \mathrm { Cu } {/tex}

{tex} \left( \mathrm { NH } _ { 4 } \right) _ { 2 } \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } \longrightarrow \mathrm { N } _ { 2 } + \mathrm { Cr } _ { 2 } \mathrm { O } _ { 3 } + 4 \mathrm { H } _ { 2 } \mathrm { O } {/tex}

Explanation

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Q 5. Which of the following relations is incorrect?

A

{tex} 3 \mathrm { NAl } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } = 0.5 \mathrm { MAl } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } {/tex}

B

{tex} 3 \mathrm { M } \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } = 6 \mathrm { NH } _ { 2 } \mathrm { SO } _ { 4 } {/tex}

{tex} 1 \mathrm { M } \mathrm { H } _ { 3 } \mathrm { PO } _ { 4 } = 1 / 3\space \mathrm { N } \mathrm { H } _ { 3 } \mathrm { PO } _ { 4 } {/tex}

D

{tex} 1 \mathrm { MAl } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } = 6 \mathrm { NAl } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } {/tex}

Explanation

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Q 6. Temporary hardness is due to {tex} \mathrm { HCO } ^ { 3 - } {/tex} of {tex} \mathrm { Mg } ^ { 2 + } {/tex} and {tex} \mathrm { Ca } ^ { 2 + } {/tex} . It is removed by addition of {tex} \mathrm { CaO } {/tex} .
{tex} \mathrm { Ca } \left( \mathrm { HCO } _ { 3 } \right) _ { 2 } + \mathrm { CaO } \rightarrow 2 \mathrm { CaCO } _ { 3 } + \mathrm { H } _ { 2 } \mathrm { O } {/tex}
Mass of CaO required to precipitate {tex}2 \mathrm { g } \mathrm { CaCO } _ { 3 } {/tex} is

A

2

0.56{tex} g {/tex}

C

0.28{tex} g {/tex}

D

1.12{tex} { g } {/tex}

Explanation

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Q 7. Bottle (A) contains 320{tex} \mathrm { mL } {/tex} of {tex} \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} solution and labelled with 10{tex} \ \mathrm{V} \ \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} and bottle (B) contains 80{tex} \mathrm { mL } {/tex} {tex} \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} having normality 5{tex} \mathrm { N } {/tex} . Bottle (A) and bottle (B) are mixed and solution filled in bottle (C). Select the correct label for bottle (C) in terms of volume strength and in terms of glitre.

{tex} 13.6 \, \mathrm { V } {/tex} and {tex} \mathrm {41.285 g } / \mathrm { L } {/tex}

B

{tex} 11.2 \, \mathrm { V } {/tex} and {tex} \mathrm {0.68 g } / \mathrm { L } {/tex}

C

{tex} 5.6 \, \mathrm {V} {/tex} and {tex} \mathrm {0.68 g } / \mathrm { L } {/tex}

D

{tex}5.6 \, {V}{/tex} and {tex} \mathrm {41.285 g } / \mathrm { L } {/tex}

Explanation

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Q 8. 1 mol of iron (Fe) reacts completely with 0.65{tex} \mathrm { mol } \ \mathrm { O } _ { 2 } {/tex} to give a mixture of only {tex} \mathrm { FeO } {/tex} and {tex} \mathrm { Fe } _ { 2 } \mathrm { O } _ { 3 } . {/tex} Mole ratio of ferrous oxide to ferric oxide is

A

{tex} 3 : 2 {/tex}

{tex} 4 : 3 {/tex}

C

{tex} 20 : 13 {/tex}

D

none of these

Explanation

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Q 9. The number of moles of {tex} \mathrm { CaCl } _ { 2 } {/tex} needed to react with excess of {tex} \mathrm { AgNO } _ { 3 } {/tex} to produce 4.31{tex} \mathrm { g } {/tex} of AgCl.

A

0.03

0.015

C

0.045

D

0.06

Explanation

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Q 10. If ten volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many volumes of water vapour would be

10

B

20

C

48

D

12

Explanation

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Q 11. 1.60 g of a metal were dissolved in {tex}\mathrm {HNO}_ { 3 } {/tex} to prepare its nitrate. The nitrate on strong heating gives 2 g oxide. The equivalent weight of metal is

A

16

32

C

48

D

12

Explanation

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Q 12. Which of the following is a redox reaction?

A

{tex} 2 \mathrm { CrO } _ { 4 } ^ { 2 - } + 2 \mathrm { H } ^ { + } \rightarrow \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - } + \mathrm { H } _ { 2 } \mathrm { O } {/tex}

B

{tex} \mathrm { CuSO } _ { 4 } + 4 \mathrm { NH } _ { 3 } \rightarrow \left[ \mathrm { Cu } \left( \mathrm { NH } _ { 3 } \right) _ { 4 } \right] \mathrm { SO } _ { 4 } {/tex}

{tex} \mathrm { Na } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 3 } + \mathrm { I } _ { 2 } \rightarrow \mathrm { Na } _ { 2 } \mathrm { S } _ { 4 } \mathrm { O } _ { 6 } + \mathrm { NaI } {/tex}

D

{tex} \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - } + 2 \mathrm { OH } ^ { - } \rightarrow 2 \mathrm { CrO } _ { 4 } ^ { 2 - } + \mathrm { H } _ { 2 } \mathrm { O } {/tex}

Explanation

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Q 13. In the reaction
{tex} x \mathrm { HI } + y \mathrm { HNO } _ { 3 } \longrightarrow \mathrm { NO } + \mathrm { I } _ { 2 } + \mathrm { H } _ { 2 } \mathrm { O } {/tex}

A

{tex} x = 3 , y = 2 {/tex}

B

{tex} x = 2 , y = 3 {/tex}

{tex} x = 6 , y = 2 {/tex}

D

{tex} x = 6 , y = 1 {/tex}

Explanation

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Q 14. In the reaction {tex} \mathrm { CrO } _ { 5 } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \rightarrow \mathrm { Cr } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } + \mathrm { H } _ { 2 } \mathrm { O } + \mathrm { O } _ { 2 } {/tex} one mole of {tex} \mathrm { CrO } _ { 5 } {/tex} will liberate how many moles of {tex} \mathrm { O } _ { 2 } ? {/tex}

A

{tex}5 / 2 {/tex}

B

{tex}5 / 4 {/tex}

C

{tex}9 / 2 {/tex}

{tex}7 / 4 {/tex}

Explanation

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Q 15. One gram of {tex} \mathrm { Na } _ { 3 } \mathrm { AsO } _ { 4 } {/tex} is boiled with excess of solid {tex} \mathrm { KI } {/tex} in presence of strong {tex}\mathrm {HCl}{/tex}. The iodine evolved is absorbed in {tex} \mathrm { KI } {/tex} solution and titrated against 0.2{tex} \mathrm { N } {/tex} hyposolution. Assuming the reaction to be
{tex} \mathrm { AsO } _ { 4 } ^ { 3 - } + 2 \mathrm { H } ^ { + } + 2 \mathrm { I } ^ { - } \longrightarrow \mathrm { AsO } _ { 3 } ^ { 3 - } + \mathrm { H } _ { 2 } \mathrm { O } + \mathrm { I } _ { 2 } {/tex}
calculate the volume of thiosulphate hypo consumed. [Atomic weight of {tex} \mathrm { As } = 75 ] {/tex}

48.1{tex} \mathrm { mL } {/tex}

B

38.4{tex} \mathrm { mL } {/tex}

C

24.7{tex} \mathrm { mL } {/tex}

D

30.3{tex} \mathrm { mL } {/tex}

Explanation



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Q 16. {tex}25 \mathrm { mL } {/tex} of {tex} 0.50\mathrm { M } \ \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} solution is added to {tex} 50\mathrm { mL } {/tex} of {tex}0.20 \mathrm { M } \ \mathrm { KMnO } _ { 4 } {/tex} in acid solution. Which of the following statement is true:

A

{tex}0.010{/tex} mole of oxygen is liberated.

{tex}0.005{/tex} mole of {tex} \mathrm { KMnO } _ { 4 } {/tex} are left.

C

{tex}0.030{/tex} g atom of oxygen gas is evolved.

D

{tex}0.0025{/tex} mole {tex} \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} does not react with {tex} \mathrm { KMnO } _ { 4 } {/tex}

Explanation

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Q 17. The molar ratio of {tex} \mathrm { Fe } ^ { + + } {/tex} to {tex} \mathrm { Fe } ^ { + + + } {/tex} in a mixture of {tex} \mathrm { FeSO } _ { 4 } {/tex} and {tex} \mathrm { Fe } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 } {/tex} having equal number of sulphate ion in both ferrous and ferric sulphate is

A

{tex} 1 : 2 {/tex}

{tex} 3 : 2 {/tex}

C

{tex} 2 : 3 {/tex}

D

Cannot be determined

Explanation

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Q 18. {tex} 28 \mathrm { NO } _ { 3 } ^ { - } + 3 \mathrm { As } _ { 2 } \mathrm { S } _ { 3 } + 4 \mathrm { H } _ { 2 } \mathrm { O } \rightarrow 6 \mathrm { AsO } _ { 4 } ^ { 3 - } + 28 \mathrm { NO } + 9 \mathrm { SO } _ { 4 } ^ { 2 - } + \mathrm { H } ^ { + } {/tex}
What will be the equivalent mass of {tex} \mathrm { As } _ { 2 } \mathrm { S } _ { 3 } {/tex} in above reaction?

A

{tex} \frac { \text { Molecular weight } } { 2 } {/tex}

B

{tex} \frac { \text { Molecular weight } } { 4 } {/tex}

C

{tex} \frac { \text { Molecular weight } } { 24 } {/tex}

{tex} \frac { \text { Molecular weight } } { 28 } {/tex}

Explanation

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Q 19. Which of the following solutions will exactly oxidise 25{tex} \mathrm { mL } {/tex} of an acid solution of 0.1{tex} \mathrm { M } \, \mathrm { Fe }{\text{ (II)}} {/tex} oxalate?

A

25{tex} \mathrm { mL } {/tex} of 0.1{tex} \mathrm { M } \ \mathrm { KMnO } _ { 4 } {/tex}

B

25{tex} \mathrm { mL } {/tex} of 0.2{tex} \mathrm { M } \ \mathrm { KMnO } _ { 4 } {/tex}

C

25{tex} \mathrm { mL } {/tex} of 0.6{tex} \mathrm { M } \ \mathrm { KMnO } _ { 4 } {/tex}

15{tex} \mathrm { mL } {/tex} of 0.1{tex} \mathrm { M } \ \mathrm { KMnO } _ { 4 } {/tex}

Explanation

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Q 20. 35{tex} \mathrm { mL } {/tex} sample of hydrogen peroxide gives of 500{tex} \mathrm { mL } {/tex} of {tex} \mathrm { O } _ { 2 } {/tex} at {tex} 27 ^ { \circ } \mathrm { C } {/tex} and 1 atm pressure. Volume strength of {tex} \mathrm { H } _ { 2 } \mathrm { O } _ { 2 } {/tex} sample will be

A

10 volume

13 volume

C

11 volume

D

12 volume

Explanation

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Q 21. The mass of oxalic acid crystals {tex} \left( \mathrm { H } _ { 2 } \mathrm { C } _ { 2 } \mathrm { O } _ { 4 } \cdot 2 \mathrm { H } _ { 2 } \mathrm { O } \right) {/tex} required to prepare 50{tex} \mathrm { mL } {/tex} of a 0.2{tex} \mathrm { N } {/tex} solution is

A

4.5{tex} \mathrm g {/tex}

B

6.3{tex} \mathrm g {/tex}

0.63{tex} \mathrm g {/tex}

D

0.45{tex} { \mathrm g } {/tex}

Explanation

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Q 22. Volume {tex} \mathrm { V } _ { 1 } \mathrm { mL } {/tex} of {tex}0.1 \mathrm { M \, K } _ { 2 } \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } {/tex} is needed for complete oxidation of {tex} 0.678\mathrm { g } \ \mathrm { N } _ { 2 } \mathrm { H } _ { 4 } {/tex} in acidic medium. The volume of {tex} 0.3\mathrm { M } \, \mathrm { KMnO } _ { 4 } {/tex} needed for same oxidation in acidic medium will be

{tex} \frac { 2 } { 5 } \mathrm { V } _ { 1 } {/tex}

B

{tex} \frac { 5 } { 2 } \mathrm { V } _ { 1 } {/tex}

C

{tex}113 \mathrm { V } _ { 1 } {/tex}

D

can't say

Explanation

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Q 23. 25.4{tex} \mathrm { g } {/tex} of iodine and 12.2{tex} \mathrm { g } {/tex} of chlorine are made to react completely to yield a mixture of {tex}\mathrm {ICl}{/tex} and {tex} \mathrm { ICl } _ { 3 } {/tex} . Calculate the ratio of moles of {tex} \mathrm { ICl } {/tex} and {tex} \mathrm { ICl } _ { 3 } {/tex} .

{tex} 1 : 1 {/tex}

B

{tex} 1 : 2 {/tex}

C

{tex} 1 : 3 {/tex}

D

{tex} 2 : 3 {/tex}

Explanation

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Q 24. A {tex}0.1097 \mathrm g {/tex} sample of {tex} \mathrm { As } _ { 2 } \mathrm { O } _ { 3 } {/tex} required {tex} 36.10\mathrm { mL } {/tex} of {tex} \mathrm { KMnO } _ { 4 } {/tex} solution for its titration. The molarity of {tex} \mathrm { KMnO } _ { 4 } {/tex} solution is

A

0.02

B

0.04

0.0122

D

0.3

Explanation

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Q 25. {tex} \mathrm { NaIO } _ { 3 } {/tex} reacts with {tex} \mathrm { NaHSO } _ { 3 } {/tex} according to equation
{tex} \mathrm { IO } _ { 3 } ^ { - } + 3 \mathrm { HSO } _ { 3 } ^ { - } \longrightarrow \mathrm { I } ^ { - } + 3 \mathrm { H } ^ { + } + 3 \mathrm { SO } _ { 4 } ^ { 2 - } {/tex}
The weight of {tex} \mathrm { NaHSO } _ { 3 } {/tex} required to react with {tex} 100\mathrm { mL } {/tex} of solution containing {tex}0.68 \mathrm { g } {/tex} of {tex} \mathrm { NaIO } _ { 3 } {/tex} is

A

5.2{tex} \mathrm g {/tex}

0.2143{tex} \mathrm { g } {/tex}

C

2.3{tex} \mathrm g {/tex}

D

None of these

Explanation