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Redox Reactions

NEET 2018MCQHard📈 Topic in 25% papers+4−1
Ques. 1NEET 2018

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

Answer

(4) HBrO

Solution

A species disproportionates when E cell = E right - E left > 0 (it is reduced as well as oxidised).

BrO3-: E cell = 1.5 - 1.82 = -0.32 V (no)

HBrO: E cell = 1.595 - 1.5 = +0.095 V (yes)

Br2: E cell = 1.0652 - 1.595 = -0.53 V (no)

BrO4- is in the highest oxidation state (+7) ⇒ it cannot be oxidised further.

∴ HBrO disproportionates: 2HBrO Br2 + BrO3- (unbalanced form).

Answer: (4)

Keep practising — Redox Reactions

Ques. 2NEET 2018

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
Ques. 3NEET 2018

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
Ques. 4AIPMT 2015

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
Ques. 5AIPMT 2015 (Cancelled)

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.
Ques. 6AIPMT 2014

The pair of compounds that can exist together is

  1. FeCl3, SnCl2
  2. HgCl2, SnCl2
  3. FeCl2, SnCl2
  4. FeCl3, KI
Ques. 7AIPMT 2014

In acidic medium, H2O2 changes Cr2O72- to CrO5 which has two (-O-O-) bonds. Oxidation state of Cr in CrO5 is

  1. +5
  2. +3
  3. +6
  4. -10
Ques. 8AIPMT 2012 (Prelims)

When Cl2 gas reacts with hot and concentrated sodium hydroxide solution, the oxidation number of chlorine changes from

  1. zero to +1 and zero to −5
  2. zero to −1 and zero to +5
  3. zero to −1 and zero to +3
  4. zero to +1 and zero to −3
Ques. 9AIPMT 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?

  1. S
  2. H
  3. Cl
  4. C
Ques. 10AIPMT 2012 (Prelims)

In which of the following compounds, nitrogen exhibits highest oxidation state?

  1. N2H4
  2. NH3
  3. N3H
  4. NH2OH
Ques. 11AIPMT 2009

Oxidation numbers of P in PO43-, of S in SO42- and that of Cr in Cr2O72- are respectively

  1. +3, +6 and +5
  2. +5, +3 and +6
  3. –3, +6 and +6
  4. +5, +6 and +6

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