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Redox Reactions · Question 5

NEET (UG) 2023MCQMedium📈 Topic in 12% papers+4−1
1

On balancing the given redox reaction, a Cr2O72-(aq) + b SO32-(aq) + cH+(aq) 2a Cr3+(aq) + b SO42-(aq) + c2H2O( ) the coefficients a, b and c are found to be, respectively -

  1. 3, 8, 1
  2. 1, 8, 3
  3. 8, 1, 3
  4. 1, 3, 8

Answer

(4) 1, 3, 8

Solution

Cr: +6 +3, gain of 3e- per Cr 6e- per Cr2O72-

S: +4 +6, loss of 2e- per SO32-

Cr2O72- : SO32- = 1 : 3, so a = 1, b = 3

Charge balance: -2 - 6 + c = +6 - 6

c = 8 (and c2 = 4 H2O)

Cr2O72- + 3SO32- + 8H+

2Cr3+ + 3SO42- + 4H2O

Answer: (4)

NEET (UG) 2023

Keep practising — Redox Reactions

2

Which of the following reactions is a decomposition redox reaction?

  1. P4(s) + 3OH-(aq) + 3H2O(l) PH3(g) + 3H2PO2-(aq)
  2. 2Pb(NO3)2(s) 2PbO(s) + 4NO2(g) + O2(g)
  3. N2(g) + O2(g) 2NO(g)
  4. Cl2(g) + 2OH-(aq) ClO-(aq) + Cl-(aq) + H2O(l)
NEET (UG) 2022 (Phase 2)
3

Which of the following reactions is the metal displacement reaction? Choose the right option.

  1. 2Pb(NO3)2 2PbO + 4NO2 + O2
  2. 2KClO3 2KCl + 3O2
  3. Cr2O3 + 2Al Al2O3 + 2Cr
  4. Fe + 2HCl FeCl2 + H2
NEET (UG) 2021
4

What is the change in oxidation number of carbon in the following reaction? CH4(g) + 4Cl2(g) CCl4(l) + 4HCl(g)

  1. 0 to +4
  2. -4 to +4
  3. 0 to -4
  4. +4 to +4
NEET (UG) 2020
5

Which of the following reactions are disproportionation reaction? Select the correct option from the following :

  1. A, C and D
  2. A and B only
  3. A and D only
  4. A, B and C
NEET (UG) 2019
6

Consider the change in oxidation state of bromine corresponding to different emf values as shown in the given diagram : BrO4- 1.82 V BrO3- 1.5 V HBrO 1.595 V Br2 1.0652 V Br- Then the species undergoing disproportionation is :

  1. BrO4-
  2. BrO3-
  3. Br2
  4. HBrO
NEET 2018
7

The correct order of N-compounds in its decreasing order of oxidation states is

  1. HNO3, NO, N2, NH4Cl
  2. HNO3, NO, NH4Cl, N2
  3. HNO3, NH4Cl, NO, N2
  4. NH4Cl, N2, NO, HNO3
NEET 2018
8

For the redox reaction, MnO4- + C2O42- + H+ Mn2+ + CO2 + H2O The correct coefficients of the reactants for the balanced equation are

  1. array|c|c|c| MnO4- & C2O42- & H+ \ 16 & 5 & 2 \ array
  2. array|c|c|c| MnO4- & C2O42- & H+ \ 2 & 5 & 16 \ array
  3. array|c|c|c| MnO4- & C2O42- & H+ \ 2 & 16 & 5 \ array
  4. array|c|c|c| MnO4- & C2O42- & H+ \ 5 & 16 & 2 \ array
NEET 2018
9

Assuming complete ionisation, same moles of which of the following compounds will require the least amount of acidified KMnO4 for complete oxidation?

  1. FeSO3
  2. FeC2O4
  3. Fe(NO2)2
  4. FeSO4
AIPMT 2015
10

Which of the following processes does not involve oxidation of iron?

  1. Formation of Fe(CO)5 from Fe.
  2. Liberation of H2 from steam by iron at high temperature.
  3. Rusting of iron sheets.
  4. Decolourisation of blue CuSO4 solution by iron.
AIPMT 2015 (Cancelled)
11

The pair of compounds that can exist together is

  1. FeCl3, SnCl2
  2. HgCl2, SnCl2
  3. FeCl2, SnCl2
  4. FeCl3, KI
AIPMT 2014

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