Redox Reactions Test

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Redox Reactions Test - 11

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Weekly Quiz Competition

Question 1
1 / -0

When a sulphur atom becomes a sulphide ion

A
There is no change in the composition of atom

B
It gains two electrons

C
The mass number changes

D
None of these

Solution

\(S + 2e^- \rightarrow S^{2-}\)
Question 2
1 / -0

In the course of a chemical reaction an oxidant

A
Loses electrons

B
Gains electrons

C
Both loses and gains electron

D
Electron change takes place

Solution

Any substance which is capable of oxidising other substances and is capable of accepting/gaining electron during oxidation is called oxidising agent or oxidant.
Question 3
1 / -0

When sodium metal is dissolved in liquid ammonia, blue colour solution is formed. The blue colour is due to

A
Solvated \(Na^+\) ions

B
Solvated electrons

C
Solvated \(NH^-_2\) ions

D
Solvated protons

Solution

When sodium metal is dissolved in liquid ammonia to form coloured solution. Dilute solutions are bright blue in colour due to the presence of solvated electrons.

\(Na + (x + y)NH_3\) → \([Na(NH_3)x]^+ + [e(NH_3)y]^-\)

Blue Colour
Question 4
1 / -0

In the reaction \(C_2O^{2-}_4 + MnO^-_4 + H^+\) → \(Mn^{2+} + CO_2 + H_2O\) the reluctant is

A
\(C_2O^{2-}_4\)

B
\(MnO^-_4\)

C
\(Mn^{2+}\)

D
\(H^+\)

Solution

\(C_2O_4^{2-} + MnO_4^- + H^+\) → \(Mn^{2+} + CO_2 + H_2O\)

In this reaction \(C_2O^{2-}_4\) act as a reducing agent.
Question 5
1 / -0

Which of the following is the most powerful oxidizing agent?

A
\(F_2\)

B
\(Cl_2\)

C
\(Br_2\)

D
\(I_2\)

Solution

Fluorine is a most powerful oxidizing agent because it consists of \(E_o\) = +2.5 volt.
Question 6
1 / -0

The strongest reducing agent is

A
\(HNO_2 \)

B
\(H_2S\)

C
\(H_2SO_3\)

D
\(SnCl_2\)

Solution

Hydrogen sulphide (\(H_2S\)) acts as strong reducing agent as it decomposes by evolving hydrogen.
Question 7
1 / -0

If 1.2 g of metal displaces 1.12 litre hydrogen at normal temperature and pressure, equivalent weight of metal would be

A
24

B
12

C
1.2, 11.2

D
1.2 ,- 11.2

Solution

1.12 ltr \(H_2\) = 1.2g;

\(\therefore\) 22.4 ltr \(H_2\) = 24g
Question 8
1 / -0

Prevention of corrosion of iron by zinc coating is called

A
Galvanization

B
Cathodic protection

C
Electrolysis

D
Photoelectrolysis

Solution

Prevention of corrosion of iron by zinc coating is called Galvanization.
Question 9
1 / -0

The compound which could not act both as oxidising as well as reducing agent is

A
\(SO_2\)

B
\(MnO_2\)

C
\(Al_2O_3\)

D
\(CrO\)

Solution

\(Al_2O_3\) could not act as a oxidising and reducing agent.
Question 10
1 / -0

\(M^{+3}\) ion loses \(3e^-\). Its oxidation number will be

A
0

B
+3

C
+6

D
-3

Solution

2 x No. of \(e^-\) losses = Oxidation no.

\(2 \times 3e^- = +6\)
Question 11
1 / -0

In which of the following compounds is the oxidation number of iodine is fractional

A
\(IF_3\)

B
\(IF_2\)

C
\(I^-_3 \)

D
\(IF_7\)

Solution

3x = -1

x = \(- \frac{1}{3}\)
Question 12
1 / -0

The number of moles of \(KMnO_4\) reduced by one mole of KI in alkaline medium is

A
One fifth

B
Five

C
One

D
Two

Solution

In alkaline medium

\(2KMnO_4 + KI + H_2O\) → \(2MnO_2 + 2KOH + KIO_3\)
Question 13
1 / -0

One mole of \(N_2H_4\) loses 10 moles of electrons to form a new compound, y. Assuming that all nitrogen appears in the new compound, what is the oxidation state of nitrogen in y (There is no change in the oxidation state of hydrogen)

A
-1

B
-3

C
+3

D
+5

Solution

\(\overset{-4}{N_2}\overset{+4}{H_4}\) \(\underset{N}{\stackrel{loss\;of\;10e^-}{\longrightarrow}}\) \(\overset{+6}{N_2}\)

O.N. of N changes from -2 to +3

1 mole of hydrazine contains 2 moles of N and loses 10 moles of electrons. Hence, 1 N atom will lose 5 electrons. Hence, its oxidation number will increase by 5. Hence, the oxidation number of N in compound A will be −2+5=+3
Question 14
1 / -0

The equivalent mass of oxidising agent in the following reaction is \(SO_2 + 2H_2S\) → \(3S + 2H_2O\)

A
32

B
64

C
16

D
8

Solution

\(SO_2\) is an oxidising agent \(4e^- + SO_2 \rightarrow S\)

Equivalent of \(SO_2\)

= \(\frac{64}{4}\)

= 16
Question 15
1 / -0

When \(SO_2\) is passed through acidified solution of potassium dichromate, then chromium sulphate is formed. The change in valency of chromium is

A
+4 to +2

B
+5 to +3

C
+6 to +3

D
+7 to +2

Solution

\(K_2Cr_2O_7 + 3SO_2 + 4H_2SO_4\) → \(K_2SO_4 + Cr_2(SO_4)_3\) \(+ 3SO_3 + 4H_2O\)
Question 16
1 / -0

Oxidation involves

A
Loss of electrons

B
Gain of electrons

C
Increase in the valency of negative part

D
Decrease in the valency of positive part

Solution

It is the process in which electrons are lost (de-electronation).
Question 17
1 / -0

The conversion of sugar \(\mathrm {C_{12}H_{22}O_{11}}\)→ \(\mathrm {CO_2}\) is

A
Oxidation

B
Reduction

C
Neither oxidation nor reduction

D
Both oxidation and reduction

Solution

In this reaction oxidation occurs.
Question 18
1 / -0

Which of the following is Redox Reaction?

A
\(\mathrm{H_2SO_4}\) with NaOH

B
In atmosphere, \(O_3\) from \(O_2\) by lightning

C
Evaporation of \(\mathrm{H_2O}\)

D
Nitrogen oxides from nitrogen and oxygen by lightning

Solution

\(2\overset{0}{N_2} + \overset{0}{O_2} \rightarrow 2\overset{+2}{N} \overset{-2}{O}\)

Here O.N. of N increases from O in \(N_2\) to +2 in \(NO_2\) and that of decreased from O in \(O_2\) to -2 in O; therefore, it is a Redox reaction.
Question 19
1 / -0

When iron or zinc is added to \(CuSO_4\) solution, copper is precipitated. It is due to

A
Oxidation of \(Cu^{+2}\)

B
Reduction of \(Cu^{+2}\)

C
Hydrolysis of \(CuSO_4\)

D
Ionization of \(CuSO_4\)

Solution

\(\overset{0}{Zn} + \overset{+2}{Cu}SO_4 \rightarrow\) \(ZnSO_4 + \overset{0}{Cu}\)

In this reaction \(Cu^{2+}\) changes in \(\overset{o}{Cu}\), hence it is called as reduction reaction.
Question 20
1 / -0

Which halide is not oxidised by \(MnO_2\)

A
F

B
Cl

C
Br

D
I

Solution

Fluorine has highest \(E^o\) value and more reactive than \(MnO_2\).

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Redox Reactions Test - 11

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Redox Reactions Test - 11

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Question 1

There is no change in the composition of atom

It gains two electrons

The mass number changes

None of these

Solution

Question 2

Loses electrons

Gains electrons

Both loses and gains electron

Electron change takes place

Solution

Question 3

Solvated \(Na^+\) ions

Solvated electrons

Solvated \(NH^-_2\) ions

Solvated protons

Solution

Question 4

\(C_2O^{2-}_4\)

\(MnO^-_4\)

\(Mn^{2+}\)

\(H^+\)

Solution

Question 5

\(F_2\)

\(Cl_2\)

\(Br_2\)

\(I_2\)

Solution

Question 6

\(HNO_2 \)

\(H_2S\)

\(H_2SO_3\)

\(SnCl_2\)

Solution

Question 7

24

12

1.2, 11.2

1.2 ,- 11.2

Solution

Question 8

Galvanization

Cathodic protection

Electrolysis

Photoelectrolysis

Solution

Question 9

\(SO_2\)

\(MnO_2\)

\(Al_2O_3\)

\(CrO\)

Solution

Question 10

0

+3

+6

-3

Solution

Question 11

\(IF_3\)

\(IF_2\)

\(I^-_3 \)

\(IF_7\)

Solution

Question 12

One fifth

Five

One

Two

Solution