Which of the following is not oxidizing agent?

Na⁺
[CrO₄]^2–
[MnO4]^–
Ozone

Solution

Na+has a stable configuration of inert gas Ne, thus it can neither lose nor gain e. hence does not undergo oxidation or reduction.

The compound that can work bot has an oxidising as well as a reducing agent is

KMnO₄
H₂SO₄
BaO₂
H₂O₂

Solution

In H₂O₂ the O.N. of O is –1 which can be increased to 0 or decresed to –2 hence H₂O₂ can work as reducing and oxidising agent.

When KMnO₄ acts as an oxidising agent and ultimately forms \(MnO_{4}^{-2}\), MnO₂, Mn₂O₃ and Mn⁺², then the number of electrons transferred in each case respectively is

4, 3, 1, 5
1, 5, 3, 7
1, 3, 4, 5
3, 5, 7, 1

Solution

In KMnO₄ the O.N. of Mn is +7, in \(MnO_{4}^{-2}\) +6, in MnO₂ +4 in Mn₂O₃ +3 and in Mn²⁺ is +2. The difference being 1, 3, 4 and 5 respectively.

Oxidation state of phosphorus in \(PO_{4}^{3-}\),P₄O₁₀ and \(P_{2}O_{7}^{4-}\) is :

+ 3
+ 2
– 3
+ 5

Solution

In \(PO_{4}^{3-}\) : x + 4(–2) = –3 ⇒ x = +5
In P₄O₁₀

Solution

In (a), (b) and (c) H₂O₂ acts as oxidising agent

Co(s) + Cu²⁺(aq) ⟶ Co²⁺(aq) + Cu(s)
The above reaction is :

Oxidation reaction
Reduction reaction
Redox reaction
None of these

Solution

This reaction is a redox reaction as Co undergoes oxidation whereas Cu⁺² undergoes reduction.

Solution

2KBr + I₂ ⟶ 2KI + Br₂ reaction is not possible because Br– ion is not oxidised in Br₂ with I₂ due to higher electrode (oxidation)potential of I₂ than bromine.

Which of these substances is a good reducing agent?

HI
KBr
FeCl₃
KClO

Solution

All the given compounds ionise in solution as
HI ⟶ H⁺ + I^-
KBr ⟶ K⁺ +Br^-
FeCl₃ ⟶ Fe³⁺ + 3Cl^-
KClO ⟶ K⁺ +ClO^-
A reducing agent is one which get oxidised easily and in this process, reducing agent provides the electrons for reduction of the other substance. Out of these given ions I^-, Br^- and Cl^- are in –1 oxidation state whereas in ClO^-, Cl is in +1 oxidation state. ClO^- ion can get,oxidised in solution to ClO₂, \(ClO_{3}^{-}\) \(ClO_{4}^{-}\) ions increasing the oxidation state to +4, +5 and +7 state which are more stable. Hence, it acts as a good reducing agent.

Which substance serves as reducing agent in the following reaction ?

14H⁺ + \(Cr_{2}O_{7}^{2-}\) + 3Ni ⟶ 2Cr³⁺ + 7H₂O + 3Ni²⁺

H₂O
Ni
H⁺
\(Cr_{2}O_{7}^{2-}\)

Solution

The compound undergo oxidation itself and reduces others is known as reducing agent. In this reaction O.N. of Ni changes from 0 to + 2 and hence Ni acts as a reducing agent.

\(CrO_{4}^{-2}\)aq. + 2H⁺ ⟶ \(CrO_{7}^{-2}\)(aq.) + H₂O Element oxidised is

Oxygen
H
Chromium
None

Solution

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