Assertion :- $\mathrm{Fe}^{3+}$ catalysts oxidation of $\mathrm{I}^{-}$ by $\mathrm{S}_2 \mathrm{O}_8^{2-}$ Reason :- $\mathrm{S}_2 \mathrm{O}_8^{2-}$ oxidize $\mathrm{Fe}^{2+}$ to $\mathrm{Fe}^{3+}$

If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion

If both Assertion & Reason are False

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JEE • CHEMISTRY • REDOX REACTIONS

Redox reactions practice · Hard

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1 Hard

1 of 20

Analyzing +4 | -1

Assertion :- Bromide ion is serving as a reducing agent in the reaction.

\mathrm{MnO}_4^{-}(\mathrm{aq})+\mathrm{Br}^{-}(\mathrm{aq})+\mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{MnO}_2(\mathrm{aq})+\mathrm{BrO}_3^{-}(\mathrm{aq})+2 \mathrm{OH}^{-}(\mathrm{aq})

Reason :- Oxidation number of

\mathrm{Br}

increases from

-1

+5.

View answer and explanation

Correct option: A

If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion

Option A is correct because the bromide ion is indeed acting as a reducing agent as its oxidation number increases from -1 to +5, which is the reason for its reducing property.

2 Hard

2 of 20

Application +4 | -1

Oxidation state of '

\mathrm{V}^{\prime}

\mathrm{Rb}_4 \mathrm{Na}\left[\mathrm{HV}_{10} \mathrm{O}_{28}\right]

View answer and explanation

Correct option: A

+5

The correct answer is +5. The oxidation state of V is calculated by setting the sum of oxidation states of all elements in the compound to zero.

3 Hard

3 of 20

Analyzing +4 | -1

Following reaction describes the rusting of iron,

4 \mathrm{Fe}+3 \mathrm{O}_2 \rightarrow 4 \mathrm{Fe}^{3+}+6 \mathrm{O}^{2-}.

Which the following statements is(are) correct?

(A) This is an example of a redox reaction

(B) Metallic iron is reduced to

\mathrm{Fe}^{3+}

(C)

\mathrm{Fe}^{3+}

is an oxidizing agent

(D) Metallic iron is reducing agent

View answer and explanation

Correct option: C

A, C and D

The correct answer is A (A, C and D) because rusting of iron is a redox reaction where iron is oxidized and acts as a reducing agent, while Fe3+ formed can act as an oxidizing agent.

4 Hard

4 of 20

Analyzing +4 | -1

Assertion: When

\mathrm{Cu}_2 \mathrm{S}

is converted into

\mathrm{Cu}^{+} \,\&\, \mathrm{SO}_2

, then equivalent weight of

\mathrm{Cu}_2 \mathrm{S}

will be

\mathrm{M} / 8\,\left(\mathrm{M}=\mathrm{Mol}\right.

. wt. of

\mathrm{Cu}_2 \mathrm{S}

)
Reason:

\mathrm{Cu}^+

is converted

\mathrm{Cu}^{++}

, during this one electrons is lost.

View answer and explanation

Correct option: B

If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion

Option B is correct because both the assertion and the reason are correct, but the reason is not the correct explanation of the assertion.

5 Hard

5 of 20

Understanding +4 | -1

Oxidation states of the metal in the minerals haematite and magnetite, respectively, are

View answer and explanation

Correct option: D

III in haematite and II, III in magnetite

Option D (III in haematite and II, III in magnetite) is correct because in haematite (Fe2O3), iron is in the +3 oxidation state, and in magnetite (Fe3O4), iron is present in both +2 and +3 oxidation states.

6 Hard

6 of 20

Application +4 | -1

Number of moles of

MnO_4^ -

required to oxidize one mole of iodide ion completely in acidic medium is

View answer and explanation

Correct option: A

1/5 mole

Option A (1/5 mole) is correct because the balanced redox reaction shows that 2 moles of

MnO_4^ -

are required to oxidize 10 moles of iodide ions, thus 1/5 mole is needed for one mole of iodide.

7 Hard

7 of 20

Understanding +4 | -1

In the group-17 of the periodic table, the power of elements as oxidising agent decreases from

View answer and explanation

Correct option: A

\mathrm{F}_2 < \mathrm{Cl}_2 < \mathrm{Br}_2 < \mathrm{I}_2

Option B (

\mathrm{I}_2 < \mathrm{Br}_2 < \mathrm{Cl}_2 < \mathrm{F}_2

) is correct because the oxidizing power of halogens decreases down the group due to decreasing electronegativity and increasing atomic size.

8 Hard

8 of 20

Application +4 | -1

For the reaction,

2 \mathrm{A}+\mathrm{B} \rightarrow 3 \mathrm{C},

when 8 moles of

\mathrm{A}

react with 5 moles of

\mathrm{B},

the maximum amount of moles of

\mathrm{C}

formed is

View answer and explanation

Correct option: C

12 moles

The correct answer is C (12 moles) because it is determined by identifying the limiting reactant and using stoichiometry.

9 Hard

9 of 20

Remembering +4 | -1

Turn bull’s blue is :

View answer and explanation

Correct option: A

\mathrm{F}{\mathrm{e}_3}{\left[ {\mathrm{Fe}{{\left( {\mathrm{CN}} \right)}_6}} \right]_2}

Option A (

\mathrm{F}{\mathrm{e}_3}{\left[ {\mathrm{Fe}{{\left( {\mathrm{CN}} \right)}_6}} \right]_2}

) is correct because it is the chemical formula for Turnbull's blue.

10 Hard

10 of 20

Application +4 | -1

5 g of a sample of bleaching powder is treated with excess acetic acid and KI solution. The liberated

{\mathrm{I}_2}

required 50 mL of

N/10

hypo. The percentage of available chlorine in the sample is :

View answer and explanation

Correct option: A

3.55

Option A (3.55) is correct because the percentage of available chlorine is calculated using the stoichiometry of the reaction and the volume of hypo used.

11 Hard

11 of 20

Understanding +4 | -1

Oxidants are substances which :

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because oxidants decrease in oxidation number, gain electrons, and oxidize others while reducing themselves.

12 Hard

12 of 20

Understanding +4 | -1

{Co}({s})+{Cu}^{2+}({aq}) \longrightarrow {Co}^{2+}({aq})+{Cu}({s})

The above reaction is

View answer and explanation

Correct option: C

Redox reaction

Option A (Displacement of metal by some other metal from complex ion) is correct because gold and silver are recovered by displacing them from their cyanide complexes using a more reactive metal like zinc.

13 Hard

13 of 20

Application +4 | -1

What volume of 3 molar

\mathrm{HN}{\mathrm{O}_3}

is needed to oxidise 8 g of

\mathrm{F}{\mathrm{e}^{2 + }}

\mathrm{F}{\mathrm{e}^{3 + }}

\mathrm{HN}{\mathrm{O}_3}

, gets converted to NO :

View answer and explanation

Correct option: B

16 m L

Option B (16 mL) is correct because it is calculated using the stoichiometry of the redox reaction between HNO3 and Fe²⁺, considering the change in oxidation states.

14 Hard

14 of 20

Application +4 | -1

For combustion of one mole acetone into

\mathrm{CO}_2

and

\mathrm{H}_2 \mathrm{O}

, moles of electron transferred during redox reaction :-

View answer and explanation

Correct option: B

Option B (16) is correct because the combustion of one mole of acetone requires 4 moles of oxygen, and each mole of oxygen involves the transfer of 4 moles of electrons.

15 Hard

15 of 20

Remembering +4 | -1

Solution of potassium chloride or ammonium nitrate in salt-bridge usually solidified by boiling with

View answer and explanation

Correct option: A

agar-agar

Option A (agar-agar) is correct because agar-agar is used to solidify the electrolyte solution in a salt bridge.

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16 Hard

16 of 20

Analyzing +4 | -1

Identify the substance oxidised, reduced, oxidising agent and reducing agent respectively from the following reaction.

2 \mathrm{AgBr}(s)+\mathrm{C}_6 \mathrm{H}_6 \mathrm{O}_2(a q) \longrightarrow 2 \mathrm{Ag}(s)+2 \mathrm{HBr}(a q)+\mathrm{C}_6 \mathrm{H}_4 \mathrm{O}_2(a q)

View answer and explanation

Correct option: B

\mathrm{C}_6 \mathrm{H}_6 \mathrm{O}_2, \mathrm{AgBr}, \mathrm{AgBr}, \mathrm{C}_6 \mathrm{H}_6 \mathrm{O}_2

Option B (C6H6O2, AgBr, AgBr, C6H6O2) is correct because C6H6O2 is oxidized (reducing agent) and AgBr is reduced (oxidizing agent).

17 Hard

17 of 20

Application +4 | -1

A sample of

2.5 \mathrm{~mol}

of hydrazine

\left(\mathrm{N}_2 \mathrm{H}_4\right)

loses

25 \mathrm{~mol}

of electrons on being converted to a new compound

\mathrm{X}.

Assuming that there is no loss of nitrogen in the formation of the new compound, what is the oxidation number of nitrogen in compound

\mathrm{X}?

View answer and explanation

Correct option: C

+3

Option C (+3) is correct because the oxidation number of nitrogen in the new compound X is calculated based on the electron loss and the initial oxidation state of nitrogen in hydrazine.

18 Hard

18 of 20

Analyzing +4 | -1

In basic medium,

{H_2}{O_2}

exhibits which of the following reactions?
A)

M{n^{2 + }} \to M{n^{4 + }}

\,\,\,\,\,\,\,\,\,\,

{I_2} \to {I^ - }

\,\,\,\,\,\,\,\,\,\,\,

PbS \to PbS{O_4}

Choose the most appropriate answer from the options given below.

View answer and explanation

Correct option: D

A and B

The correct answer is D (A and B) because in a basic medium, hydrogen peroxide (

H_2O_2

) can act as both an oxidizing agent (reducing

I_2

I^-

) and a reducing agent (oxidizing

Mn^{2+}

Mn^{4+}

19 Hard

19 of 20

Analyzing +4 | -1

Assertion :-

\mathrm{Fe}^{3+}

catalysts oxidation of

\mathrm{I}^{-}

\mathrm{S}_2 \mathrm{O}_8^{2-}

Reason :-

\mathrm{S}_2 \mathrm{O}_8^{2-}

oxidize

\mathrm{Fe}^{2+}

\mathrm{Fe}^{3+}

View answer and explanation

Correct option: C

If Assertion is True but the Reason is False

Option C is correct because while the assertion is true, the reason is false; Fe3+ catalyzes the reaction, but S2O82- oxidizes Fe2+ to Fe3+ not the other way around.

20 Hard

20 of 20

Application +4 | -1

5 g of a sample of bleaching powder is treated with excess acetic acid and KI solution. The liberated

{\mathrm{I}_2}

required 50 mL of

N/10

hypo. The percentage of available chlorine in the sample is :

View answer and explanation

Correct option: A

3.55

Option A (3.55) is correct because the percentage of available chlorine is calculated based on the stoichiometry of the reaction and the amount of hypo used.

Revision notes and key takeaways

Review REDOX REACTIONS in your textbook or class notes, then use this set to check your understanding.

Key Takeaways

✓ This set contains 20 single-correct-answer MCQs on REDOX REACTIONS.
✓ Try each question before opening its answer. Read the explanation where one is available.
✓ Sign in to save submitted answers. Revisit incorrect answers alongside your textbook or class notes.

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