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Redox Reactions

21 Questions
All Exams NEET AIIMS
2025 NEET MCQ
NEET 2025

Consider the following compounds :

${\mathrm{K\underline{O}}}_2, \mathrm{H}_2 \underline{\mathrm{O}}_2$ and $\mathrm{H}_2 \underline{S }O_4$

The oxidation state of the underlined elements in them are, respectively,

A.
$+1,-2$, and +4
B.
$+4,-4$, and +6
C.
$+1,-1$, and +6
D.
$+2,-2$, and +6
2024 NEET MCQ
NEET 2024 (Re-Examination)

The oxidation states not shown by Mn in given reaction is :

$ 3 \mathrm{MnO}_4^{2-}+4 \mathrm{H}^{+} \longrightarrow 2 \mathrm{MnO}_4^{-}+\mathrm{MnO}_2+2 \mathrm{H}_2 \mathrm{O} $

A. +6

B. +2

C. +4

D. +7

E. +3

Choose the most appropriate answer from the options given below :

A.
D and E only
B.
B and D only
C.
A and B only
D.
B and E only
2024 NEET MCQ
NEET 2024

Which reaction is NOT a redox reaction?

A.
$\mathrm{Zn}+\mathrm{CuSO}_4 \rightarrow \mathrm{ZnSO}_4+\mathrm{Cu}$
B.
$2 \mathrm{KClO}_3+\mathrm{I}_2 \rightarrow 2 \mathrm{KIO}_3+\mathrm{Cl}_2$
C.
$\mathrm{H}_2+\mathrm{Cl}_2 \rightarrow 2 \mathrm{HCl}$
D.
$\mathrm{BaCl}_2+\mathrm{Na}_2 \mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4+2 \mathrm{NaCl}$
2023 NEET MCQ
NEET 2023 Manipur

The correct option for a redox couple is:

A.
Both are oxidised forms involving same element.
B.
Both are reduced forms involving same element.
C.
Both the reduced and oxidised forms involve same element.
D.
Cathode and anode together.
2023 NEET MCQ
NEET 2023

On balancing the given redox reaction,

$\mathrm{aCr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{bSO}_{3}^{2-}(\mathrm{aq})+\mathrm{cH}^{+}(\mathrm{aq}) \rightarrow 2 \mathrm{aCr}^{3+}(\mathrm{aq})+\mathrm{bSO}_{4}^{2-}(\mathrm{aq})+\frac{\mathrm{c}}{2} \mathrm{H}_{2} \mathrm{O}(\ell)$

the coefficients $\mathrm{a}, \mathrm{b}$ and $\mathrm{c}$ are found to be, respectively -

A.
3, 8, 1
B.
1, 8, 3
C.
8, 1, 3
D.
1, 3, 8
2022 NEET MCQ
NEET 2022 Phase 2

Which of the following reactions is a decomposition redox reaction?

A.
P4(s) + 3OH$-$(aq) + 3H2O(l) $\to$ PH3(g) + 3H2PO$_2^ - $(aq)
B.
2Pb(NO3)2(s) $\to$ 2PbO(s) + 4NO2(g) + O2(g)
C.
N2(g) + O2(g) $\to$ 2NO(g)
D.
Cl2(g) + 2OH$-$(aq) $\to$ ClO$-$(aq) + Cl$-$(aq) + 4H2O(l)
2020 NEET MCQ
NEET 2020 Phase 1
What is the change in oxidation number of carbon in the following reaction?
CH4(g) + 4Cl2(g) $ \to $ CCl4(l) + 4HCl(g)
A.
0 to + 4
B.
$ - $4 to + 4
C.
0 to $ - $ 4
D.
+ 4 to + 4
2019 NEET MCQ
NEET 2019
Which of the following reactions are disproportionation reaction?

(a) 2Cu+ $ \to $ Cu2+ + Cu0
(b) 3MnO42+ + 4H+ $ \to $ 2MnO4- + MnO2 + 2H2O
(c) 2KMnO4 $\buildrel \Delta \over \longrightarrow $ K2MnO4 + MnO2 + O2
(d) 2MnO4- + 3Mn2+ + 2H2O $ \to $ 5MnO2 + 4${H^ \oplus }$

Select the correct option from the following :
A.
(a), (c) and (d)
B.
(a) and (b) only
C.
(a) and (d) only
D.
(a), (b) and (c)
2018 NEET MCQ
NEET 2018
The correct order of N-compounds in its decreasing order of oxidation states is
A.
HNO3 , NO, N2 , NH4Cl
B.
HNO3 , NO, NH4Cl, N2
C.
HNO3 , NH4Cl, NO, N
D.
NH4Cl, N2 , NO, HNO3
2018 NEET MCQ
NEET 2018
For the redox reaction,
MnO4– + C2O4 2– + H+ $ \to $ Mn2+ + CO2 + H2O
The correct coefficients of the reactants for the balanced equation are
A.
MnO4- C2O42- H+
16 5 2
B.
MnO4- C2O42- H+
2 5 16
C.
MnO4- C2O42- H+
2 16 5
D.
MnO4- C2O42- H+
5 16 2
2016 NEET MCQ
NEET 2016 Phase 2
Hot concentrated sulphate acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?
A.
Cu + 2H2SO4 $ \to $ CuSO4 + SO2 + 2H2O
B.
S + 2H2SO4 $ \to $ 3SO2 + 2H2O
C.
C + 2H2SO4 $ \to $ CO2 + 2SO2 + 2H2O
D.
CaF2 + H2SO4 $ \to $ CaSO4 + 2HF
2014 NEET MCQ
AIPMT 2014
(I)   H2O2 + O3 $ \to $ H2O + 2O2
(II)   H2O2 + Ag2O $ \to $ 2Ag + H2O + O2
Role of Hydrogen peroxide in the above reactions is respectvely
A.
oxidizing in (I) and reducing in (II)
B.
reducing in (I) and oxidizing (II)
C.
reducing in (I) and (II)
D.
oxidizing in (I) and (II)
2014 NEET MCQ
AIPMT 2014
In acidic medium, H2O2 changes Cr2O72- to CrO5 which has two

($-$O$-$O$-$) bonds. Oxidation state of Cr in CrO5 is
A.
+5
B.
+3
C.
+6
D.
$-$10
2014 NEET MCQ
AIPMT 2014
The pair of compounds that can exist together is
A.
FeCl3, SnCl2
B.
HgCl2, SnCl2
C.
FeCl2, SnCl2
D.
FeCl3, KI
2012 NEET MCQ
AIPMT 2012 Prelims
When Cl2 gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from
A.
zero to +1 and zero to $-$5
B.
zero to $-$1 and zero to +5
C.
zero to $-$1 and zero to +3
D.
zero to +1 and zero to $-$3
2012 NEET MCQ
AIPMT 2012 Prelims
A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes maximum change in the oxidation number?
A.
S
B.
H
C.
Cl
D.
C
2009 NEET MCQ
AIPMT 2009
Oxidation numbers of P in PO$_4^{3 - }$, of S in SO$_4^{2 - }$ and that of Cr in Cr2O$_7^{2 - }$ are respectively
A.
+3, +6 and +5
B.
+5, +3 and +6
C.
$-$3, +6 and + 6
D.
+5, +6 and +6
2008 NEET MCQ
AIPMT 2008
Number of moles of MnO$_4^{ - }$ required to oxidize one mole of ferrous oxalate completely in acidic medium will be
A.
7.5 moles
B.
0.2 moles
C.
0.6 moles
D.
0.4 moles
2004 NEET MCQ
AIPMT 2004
Which is the best description of the behaviour of bromine in the reaction given below?
H2O + Br2 $ \to $ HOBr + HBr
A.
Proton acceptor only
B.
Both oxidised and reduced
C.
Oxidised only
D.
Reduced only
2003 NEET MCQ
AIPMT 2003
The oxidation states of sulphur in the anions

SO3${_3^{2 - }}$, S2O${_4^{2 - }}$ and S2O${_6^{2 - }}$ follow the order
A.
S2O${_4^{2 - }}$ < SO${_3^{2 - }}$ < S2O${_6^{2 - }}$
B.
SO${_3^{2 - }}$ < S2O${_4^{2 - }}$ < S2O${_6^{2 - }}$
C.
S2O${_4^{2 - }}$ < S2O${_6^{2 - }}$ < SO${_3^{2 - }}$
D.
S2O${_6^{2 - }}$ < S2O${_4^{2 - }}$ < SO${_3^{2 - }}$
2019 AIIMS MCQ
AIIMS 2019

Which of the following can react with $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ ?

A.
$\mathrm{SO}_3^{-2}$
B.
$\mathrm{CO}_3^{-2}$
C.
$\mathrm{SO}_4^{-2}$
D.
$\mathrm{NO}_3^{-}$