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Redox Reactions · Question 14

AIPMT 2015 (Cancelled)MCQMedium📈 Topic in 25% papers+4−1
1

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.

Answer

(1) Formation of Fe(CO)5 from Fe.

Solution

(1) Fe + 5CO Fe(CO)5: CO is a neutral ligand ⇒ oxidation number of Fe stays 0 ⇒ no oxidation.

(2) 3Fe + 4H2O Fe3O4 + 4H2: Fe goes from 0 to +8/3 ⇒ oxidised.

(3) Rusting gives Fe2O3 xH2O: Fe goes from 0 to +3 ⇒ oxidised.

(4) Fe + CuSO4 FeSO4 + Cu: Fe goes from 0 to +2 ⇒ oxidised.

Answer: (1)

AIPMT 2015 (Cancelled)

Keep practising — Redox Reactions

2

The pair of compounds that can exist together is

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

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
AIPMT 2014
4

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
AIPMT 2012 (Prelims)
5

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
AIPMT 2012 (Prelims)
6

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

  1. N2H4
  2. NH3
  3. N3H
  4. NH2OH
AIPMT 2012 (Prelims)
7

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
AIPMT 2009
8

Number of moles of MnO4- required to oxidize one mole of ferrous oxalate completely in acidic medium will be

  1. 7.5 moles
  2. 0.2 moles
  3. 0.6 moles
  4. 0.4 moles
AIPMT 2008
9

Which is the best description of the behaviour of bromine in the reaction given below? H2O + Br2 HOBr + HBr

  1. Proton acceptor only
  2. Both oxidised and reduced
  3. Oxidised only
  4. Reduced only
AIPMT 2004
10

The oxidation states of sulphur in the anions SO32-, S2O42- and S2O62- follow the order

  1. S2O42- < SO32- < S2O62-
  2. SO32- < S2O42- < S2O62-
  3. S2O42- < S2O62- < SO32-
  4. S2O62- < S2O42- < SO32-
AIPMT 2003
11

Which reaction is not feasible?

  1. 2KI + Br2 2KBr + I2
  2. 2KBr + I2 2KI + Br2
  3. 2KBr + Cl2 2KCl + Br2
  4. 2H2O + 2F2 4HF + O2
AIPMT 2002

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