Redox Reactions Test

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Redox Reactions Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

The change $$P_{2}O_{5} \rightarrow H_{4}P_{2}O_{7}$$ is an :

A
oxidation process

B
reduction process

C
neither Oxidation nor reduction process

D
redox process

Solution

Oxidation number of $$P_2O_5$$: $$2x+(-10)=0$$
$$\Rightarrow 2x=10$$
$$\Rightarrow x=5$$.
Oxidation number of $$P$$ in $$H_4P_2O_7$$: $$4+2x+(-14)=0$$
$$\Rightarrow 2x=14-4$$
$$\Rightarrow x=5$$.
Since, oxidation is loss of electron and reduction is gain of electron and Redox reaction is when both oxidation & reduction take place simultaneously. Therefore, It is neither oxidation nor a reduction process.
Question 2
1 / -0

In $$MgCl_{2}$$, the oxidation number of chlorine is:

A
$$+1$$

B
$$+2$$

C
$$-1$$

D
$$0$$

Solution

In $$MgCl_2$$, oxidation number of $$Cl$$ is:

$$\Rightarrow 2+2x=0$$

$$\Rightarrow x=-1$$.

Hence, option C is correct.
Question 3
1 / -0

The number of moles of $$KMnO_4$$ that will be needed to react completely with one mole of ferrous oxalate in acidic medium is:

A
$$\dfrac {2}{5}$$

B
$$\dfrac {3}{5}$$

C
$$\dfrac {4}{5}$$

D
$$1$$

Solution

The balanced chemical reaction is as shown below:

$$3MnO_4^-+5FeC_2O_4+24H^+\rightarrow 3Mn^{2+}+5Fe^{3+}+10CO_2+12H_2O$$

$$3$$ moles of $$KMnO_4$$ react with $$5$$ moles of $$FeC_2O_4$$.

Hence, the number of moles of $$KMnO_4$$ that will be needed to react completely with one mole of ferrous oxalate in acidic medium is $$\dfrac {3}{5}$$.

Hence, the correct option is $$B$$
Question 4
1 / -0

In which of the following does sulphur has the lowest oxidation state?

A
$$H_2SO_4$$

B
$$SO_2$$

C
$$H_2SO_3$$

D
$$H_2S$$

Solution

(A) $$H_2SO_4$$
Let oxidation number of sulphur in $$H_2SO_4$$ be x.
$$\therefore 2+x-4(2)=0$$
$$x=+6$$
(B) $$SO_2$$
Let oxidation number of sulphur in $$SO_2$$ be x.
$$\therefore x+(2)(-2)=0$$
$$x=4$$
$$H_2SO_3$$
(C)Let oxidation number of sulphur in $$H_2SO_3$$ be x.
$$\therefore 2+x+(3)(-2)=0$$
$$x=4$$
(D)
Let oxidation number of sulphur in $$H_2S$$ be x.
$$\therefore 2+x=0$$
$$x=-2$$
Question 5
1 / -0

For the redox reaction:
$$MnO_4^-+C_2O_4^{2-}+H^+\rightarrow Mn^{2+}+CO_2+H_2O$$
The correct coefficients of the reactants $$MnO_4^-, C_2O_4^{2-}$$ and $$H^+$$ for the balanced reaction are ____, ____ and ____ respectively.

A
$$2,\: 5,\: 16$$

B
$$16,\: 5,\: 2$$

C
$$5,\: 16,\: 2$$

D
$$2,\: 16,\: 5$$

Solution
Question 6
1 / -0

The number of moles of $$KMnO_4$$ that will be needed to react with one mole of sulphite ion in acidic solution is :

A
$$\dfrac {2}{5}$$

B
$$\dfrac {3}{5}$$

C
$$\dfrac {4}{5}$$

D
$$1$$

Solution

The balanced chemical reaction is as given below,

$$2MnO_4^-+5SO_3^{2-}+6H^+\rightarrow 2Mn^{2+}+5SO_4^{2-}+3H_2O$$

$$5$$ moles of $$SO_3^{2-}$$ reacts with $$2$$ moles of $$KMnO_4$$.

Hence, $$1$$ mole of $$SO_3^{2-}$$ will react with $$\dfrac{2}{5}$$ moles of $$KMnO_4$$.
Question 7
1 / -0

Oxygen shows oxidation state of -1 in the compound :

A
$$NO_{2}$$

B
$$MnO_{2}$$

C
$$PbO_{2}$$

D
$$Na_{2}O_{2}$$

Solution

$$Na_2O2$$:
$$2+2x=0$$
$$\Rightarrow 2x=-2$$
$$\Rightarrow x=-1$$.
Question 8
1 / -0

Oxidation number of $$Cr$$ in $$CrO_2Cl_2$$ is $$+6$$. Oxidation number (per atom) of oxygen is:

A
$$-2$$

B
$$+2$$

C
$$-1$$

D
$$+1$$

Solution

Let the oxidation state of $$O$$ be $$x$$.
Since, the compound $$CrO_2Cl_2$$ is neutral, sum of oxidaton states of all elements must be zero.
Hence, $$6+2x-2=0$$ (neutral compound)
So, $$ x= -2$$
Hence, the oxidation state of $$O$$ is $$-2$$.
Question 9
1 / -0

Among the following, the number of elements showing only one non-zero oxidation state is O, Cl, F, N, P, Sn, Tl, Na, Ti

A
2

B
8

C
5

D
9

Solution

Sodium (+1) and fluorine (-1) show only one non zero oxidation state.
The oxidation states of oxygen are -1, -2 and +2.
The oxidation states of chlorine range from -1 to +7.
The oxidation states of nitrogen and phosphorus range from -3 to +5.
The oxidation states of tin range from +2 to +4.
The oxidation states of thalium are +1 and +3. +3 oxidation state is rare but does exist.
The oxidation states of titanium are +2, +3, +4 respectively.
Question 10
1 / -0

Among the following, the species in which the oxidation number of an element is $$+6$$ is :

A
$$MnO_4^-$$

B
$$Cr(CN)_6^{3-}$$

C
$$NiF_6^{2-}$$

D
$$CrO_2Cl_2$$

Solution

The oxidation number of manganese in $$MnO_4^-$$ is $$7$$.
The oxidation number of chromium in $$Cr(CN)_6^{3-}$$ is $$+3$$.
The oxidation number of nickel in $$NiF_6^{2-}$$ is $$+4$$.
The oxidation number of chromium in $$CrO_2Cl_2$$ is $$+6$$.
Hence, the species in which an element has oxidation number $$+6$$ is $$CrO_2Cl_2$$.

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Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 20

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Redox Reactions Test - 20

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Question 1

oxidation process

reduction process

neither Oxidation nor reduction process

redox process

Solution

Question 2

$$+1$$

$$+2$$

$$-1$$

$$0$$

Solution

Question 3

$$\dfrac {2}{5}$$

$$\dfrac {3}{5}$$

$$\dfrac {4}{5}$$

$$1$$

Solution

Question 4

$$H_2SO_4$$

$$SO_2$$

$$H_2SO_3$$

$$H_2S$$

Solution

Question 5

$$2,\: 5,\: 16$$

$$16,\: 5,\: 2$$

$$5,\: 16,\: 2$$

$$2,\: 16,\: 5$$

Solution

Question 6

$$\dfrac {2}{5}$$

$$\dfrac {3}{5}$$

$$\dfrac {4}{5}$$

$$1$$

Solution

Question 7

$$NO_{2}$$

$$MnO_{2}$$

$$PbO_{2}$$

$$Na_{2}O_{2}$$

Solution

Question 8

$$-2$$

$$+2$$

$$-1$$

$$+1$$

Solution

Question 9

2

8

5

9

Solution

Question 10

$$MnO_4^-$$

$$Cr(CN)_6^{3-}$$

$$NiF_6^{2-}$$

$$CrO_2Cl_2$$

Solution

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