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JEE • CHEMISTRY • REDOX REACTIONS

Redox reactions practice · Mixed difficulty

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These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 1-30 of 264 questions
1 Easy
1 of 264
Remembering +4 | -1
The oxidation number of H\mathrm{H} in sodium hydride is
View answer and explanation
Correct option: C
−1-1
Option C (-1) is correct because hydrogen has an oxidation number of -1 when bonded to a more electropositive element like sodium.
2 Medium
2 of 264
Remembering +4 | -1
A reagent, which can decrease the oxidation number of an element, is called
View answer and explanation
Correct option: C
reducing agent
Option C (reducing agent) is correct because a reducing agent donates electrons, causing another substance to have its oxidation number decreased.
3 Medium
3 of 264
Analyzing +4 | -1
Consider the following decomposition reaction

2KClO3⟶2KCl+3O22 \mathrm{KClO}_3 \longrightarrow 2 \mathrm{KCl}+3 \mathrm{O}_2

In the above reaction,
View answer and explanation
Correct option: B
chlorine is undergoing reduction
Option B is correct because chlorine's oxidation state decreases from +5 to -1, indicating reduction.
4 Medium
4 of 264
Analyzing +4 | -1
Assertion (A): HNO3\mathrm{HNO}_3 acts as oxidizing agent.

Reason (R): Oxidation no. of nitrogen is +5, no increase in oxidation no. beyond +5 can occur. The oxidation no. of HNO3\mathrm{HNO}_3 can only decrease.
View answer and explanation
Correct option: A
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
The correct answer is A because HNO3 acts as an oxidizing agent due to the nitrogen atom's ability to decrease its oxidation number from +5, and the reason correctly explains this.
5 Hard
5 of 264
Analyzing +4 | -1
Assertion :- Bromide ion is serving as a reducing agent in the reaction.

MnO4−(aq)+Br−(aq)+H2O⟶2MnO2(aq)+BrO3−(aq)+2OH−(aq)\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 Br\mathrm{Br} increases from −1-1 to +5.+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.
6 Easy
6 of 264
Remembering +4 | -1
A substance, that by its sharp colour change indicates the completion of reaction is known as :
View answer and explanation
Correct option: C
Indicator
Option A (Square of the orbital wave function i.e., ψ2\psi^2) is correct because the probability of finding an electron at a point within an atom is proportional to the square of the orbital wave function, ψ2\psi^2.
7 Medium
7 of 264
Application +4 | -1
The number of mole of ferrous oxalate oxidised by one mole of KMnO4\mathrm{KMn}{\mathrm{O}_4} is:
View answer and explanation
Correct option: D
5/35/3
Option D (5/35/3) is correct because the balanced redox reaction between ferrous oxalate and KMnO4 requires 5/3 moles of ferrous oxalate per mole of KMnO4.
8 Medium
8 of 264
Analyzing +4 | -1
Which one is not a redox titration?
View answer and explanation
Correct option: D
AgNO3vs.KCl\mathrm{AgN}{\mathrm{O}_3}vs.\mathrm{KCl}
The correct answer is D (AgNO₃ vs. KCl) because this is a precipitation reaction, not a redox reaction involving electron transfer.
9 Medium
9 of 264
Application +4 | -1
The average oxidation number of I{I} in KI3{KI}_3 and Fe{Fe} in Fe3O4{Fe}_3 {O}_4 are respectively :-
View answer and explanation
Correct option: A
−1/3,+8/3-1 / 3,+8 / 3
Option A (−1/3,+8/3-1 / 3,+8 / 3) is correct because it represents the average oxidation states calculated for I in KI3 and Fe in Fe3O4 respectively.
10 Medium
10 of 264
Application +4 | -1
In compound HN3H{N_3} (Hydrozoic acid), oxidation state of N atoms are
View answer and explanation
Correct option: B
0,−2,+10,-2,+1
Option B (0,-2,+1) is correct because the oxidation states of the three nitrogen atoms in HN3HN_3 are 0, -2, and +1, respectively, based on resonance structures.
11 Medium
11 of 264
Analyzing +4 | -1
Which of the following involves the reduction of copper?
View answer and explanation
Correct option: B
Cu2+(aq)+2I−(aq)→2CuI(aq){Cu}^{2+}(\mathrm{aq})+2 {I^-}(\mathrm{aq}) \rightarrow 2 {CuI}(\mathrm{aq})
The correct answer is B because in the reaction Cu2+(aq) + 2I-(aq) → 2CuI(aq), copper's oxidation state decreases from +2 to +1, indicating reduction.
12 Medium
12 of 264
Application +4 | -1
Fe shows an oxidation state of +1 in:
View answer and explanation
Correct option: B
[Fe(H2O)5NO]SO4\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_5 \mathrm{NO}\right] \mathrm{SO}_4
Option B ([Fe(H₂O)₅NO]SO₄) is correct because the iron in this complex has an oxidation state of +1, considering NO as NO⁺.
13 Hard
13 of 264
Application +4 | -1
Oxidation state of ' V′\mathrm{V}^{\prime} in Rb4Na[HV10O28]\mathrm{Rb}_4 \mathrm{Na}\left[\mathrm{HV}_{10} \mathrm{O}_{28}\right] is
View answer and explanation
Correct option: A
+5+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.
14 Medium
14 of 264
Remembering +4 | -1
The redox reactions are called combustion reactions which make use of
View answer and explanation
Correct option: A
elemental dioxygen
Option A (elemental dioxygen) is correct because combustion reactions are redox reactions that involve the rapid reaction of a substance with oxygen.
15 Easy
15 of 264
Analyzing +4 | -1
Statement-I: In the reaction between potassium permanganate and potassium iodide, permanganate ions act as oxidising agent.

Statement-II: Oxidation state of manganese changes from +2 to +7 during the above reaction.
View answer and explanation
Correct option: C
Statement-I is correct but statement-II is incorrect
Option C is correct. Statement-I is correct because potassium permanganate acts as an oxidizing agent. Statement-II is incorrect because the oxidation state of manganese changes from +7 to +2 (in acidic medium) or +4 (in neutral or basic medium).

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16 Hard
16 of 264
Analyzing +4 | -1
Following reaction describes the rusting of iron, 4Fe+3O2→4Fe3++6O2−.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 Fe3+\mathrm{Fe}^{3+}

(C) Fe3+\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.
17 Easy
17 of 264
Application +4 | -1
The oxidation number of hydrogen in hydrolith (CaH2)\left( {\mathbf{Ca}{\mathbf{H}_\mathbf{2}}} \right)
View answer and explanation
Correct option: B
−1- 1
Option B (-1) is correct because in metal hydrides like CaH₂, hydrogen has an oxidation state of -1.
18 Medium
18 of 264
Understanding +4 | -1
During a redox change, the oxidant K2Cr2O7{\mathrm{K}_2}\mathrm{C}{\mathrm{r}_2}{\mathrm{O}_7} is always reduced to :
View answer and explanation
Correct option: C
Cr3+\mathrm{C}{\mathrm{r}^{3 + }}
Option C is correct. During a redox reaction, dichromate (K2Cr2O7) acts as an oxidizing agent and is reduced to Cr3+.
19 Medium
19 of 264
Analyzing +4 | -1
Assuming complete ionization, same moles of which of the following compounds will require the least
Amount of acidified KMnO4\mathrm{KMn}{\mathrm{O}_\mathrm{4}} for complete oxidation?
View answer and explanation
Correct option: C
FeSO4\mathrm{FeS}{\mathrm{O}_\mathrm{4}}
Option C (FeSO4) is correct because FeSO4 requires the least amount of KMnO4 for complete oxidation as it involves the smallest change in oxidation state.
20 Easy
20 of 264
Analyzing +4 | -1
when K2Cr2O7{\mathbf{K}_\mathbf{2}}\mathbf{C}{\mathbf{r}_\mathbf{2}}{\mathbf{O}_\mathbf{7}} is converted to K2CrO4{\mathbf{K}_\mathbf{2}}\mathbf{Cr}{\mathbf{O}_\mathbf{4}} , the change in the oxidation of chromium is
View answer and explanation
Correct option: A
0
Option A is correct because the oxidation state of chromium remains +6 in both K2Cr2O7{\mathbf{K}_\mathbf{2}}\mathbf{C}{\mathbf{r}_\mathbf{2}}{\mathbf{O}_\mathbf{7}} and K2CrO4{\mathbf{K}_\mathbf{2}}\mathbf{Cr}{\mathbf{O}_\mathbf{4}}, hence the change is 0.
21 Medium
21 of 264
Understanding +4 | -1
Which one of the following is the correct match?
View answer and explanation
Correct option: D
SO2\mathrm{SO}_2 - both oxidising and reducing agent
Option D (SO2 - both oxidising and reducing agent) is correct because sulfur in SO2 has an intermediate oxidation state (+4) and can either gain or lose electrons.
22 Hard
22 of 264
Analyzing +4 | -1
Assertion: When Cu2S\mathrm{Cu}_2 \mathrm{S} is converted into Cu+ & SO2\mathrm{Cu}^{+} \,\&\, \mathrm{SO}_2, then equivalent weight of Cu2S\mathrm{Cu}_2 \mathrm{S} will be M/8 (M=Mol\mathrm{M} / 8\,\left(\mathrm{M}=\mathrm{Mol}\right.. wt. of Cu2S\mathrm{Cu}_2 \mathrm{S})
Reason: Cu+\mathrm{Cu}^+ is converted Cu++\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.
23 Medium
23 of 264
Application +4 | -1
In the following redox reactions
Cr2O72−+Fe2+ →  Fe3++Cr3+C{r_2}O_7^{2 - } + F{e^{2 + }}\,\xrightarrow{\,}\,F{e^{3 + }} + C{r^{3 + }}
1 mole of Cr2O72−C{r_2}O_7^{2 - } oxidises
View answer and explanation
Correct option: D
6  moles  of  Fe2+\mathrm{6\,\,moles\,\,of }\,\,F{e^{2 + }}
Option D (6  moles  of Fe2+\mathrm{6\,\,moles\,\,of }\,F{e^{2 + }}) is correct because 1 mole of Cr2O72−C{r_2}O_7^{2 - } requires 6 moles of Fe2+F{e^{2 + }} for complete oxidation based on the balanced redox reaction.
24 Medium
24 of 264
Understanding +4 | -1
Which of the following acts as an oxidising as well as reducing agent?
View answer and explanation
Correct option: D
NaNO2\mathrm{NaN}{\mathrm{O}_2}
The correct answer is D (NaNO2\mathrm{NaN}{\mathrm{O}_2}) because it can both accept and donate electrons, acting as both an oxidizing and reducing agent due to nitrogen's intermediate oxidation state.
25 Easy
25 of 264
Understanding +4 | -1
The highest oxidation state of Mn is shown by
View answer and explanation
Correct option: B
KMno4KMn{o_4}
Option B (KMno4KMn{o_4}) is correct because in KMnO4KMn{O_4}, manganese has an oxidation state of +7, which is its highest possible oxidation state.
26 Easy
26 of 264
Application +4 | -1
The oxidation number of N in N2H5+{\mathrm{N}_2}\mathrm{H}_5^ + is :
View answer and explanation
Correct option: A
−2- 2
Option A (-2) is correct because it accurately calculates the oxidation number of N in N2H5+.
27 Medium
27 of 264
Application +4 | -1
For the balanced redox reaction.
aMnO4−+bH2O2+cH+→dMn2++eO2+fH2O{aMnO}_4^{-}+{bH}_2 {O}_2+{cH}^{+} \rightarrow {dMn}^{2 +}+{eO}_2+{fH}_2 {O} the value of a,b,ca, b, c and ee respectively are
View answer and explanation
Correct option: B
2,5,6,52,5,6,5
The correct answer is 2,5,6,52, 5, 6, 5. Balancing the redox reaction requires determining the correct stoichiometric coefficients to ensure both mass and charge are conserved.
28 Easy
28 of 264
Application +4 | -1
Maximum oxidation state is present in :
View answer and explanation
Correct option: A
CrO2Cl2andMnO4−\mathrm{Cr}{\mathrm{O}_2}\mathrm{C}{\mathrm{l}_2}\mathrm{ and MnO}_4^ -
Option A (CrO2Cl2andMnO4−\mathrm{Cr}{\mathrm{O}_2}\mathrm{C}{\mathrm{l}_2}\mathrm{ and MnO}_4^ -) is correct because Cr in CrO2Cl2 has +6 and Mn in MnO4- has +7 oxidation states, which are the maximum for these elements.
29 Medium
29 of 264
Analyzing +4 | -1
Assertion: SO2\mathrm{SO}_2 and Cl2\mathrm{Cl}_2 both are bleaching agents.

Reason: Both are reducing agents.
View answer and explanation
Correct option: C
Assertion is true, Reason is false
Option C (Assertion is true, Reason is false) is correct because both SO2 and Cl2 are bleaching agents, but their mechanisms differ; SO2 acts as a reducing agent, while Cl2 acts as an oxidizing agent.
30 Easy
30 of 264
Application +4 | -1
The oxidation number of carbon in CH2O\mathrm{CH}_2 \mathrm{O} is:
View answer and explanation
Correct option: C
0
Option C (0) is correct because the oxidation number of carbon in CH2O is calculated by setting the sum of oxidation numbers of all atoms to zero.
Revision notes and key takeaways

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Key Takeaways

  • ✓ This set contains 264 single-correct-answer MCQs on REDOX REACTIONS.
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