Redox Reactions Test

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Redox Reactions Test - 49

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Weekly Quiz Competition

Question 1
1 / -0

In which of the following compounds iron has lowest oxidation state :-

A
$$FeSO_4(NH_4)_2SO_4.6H_2O$$

B
$$K_4[Fe(CN)_6]$$

C
$$[Fe(CO)_5]$$

D
$$Fe_{0.94}O$$

Solution
Question 2
1 / -0

Which of the following, oxidation number of carbon is -1?

A
$${ CH }_{ 4 }$$

B
$${ C }_{ 6 }{ H }_{ 6 }$$

C
$${ C }Cl_{ 4 }$$

D
$$HCHCl$$

Solution

For benzene let oxidation number of C be x,
$$6x+6\times(+1) \implies x=-1$$

The oxidation state of carbon in benzene is -1 and the oxidation state of hydrogen in benzene is +1. In a C-H bond(this bond is non-polar covalent), the H is treated as if it has an oxidation state of +1. This means that every C-H bond will decrease the oxidation state of carbon by 1.
Question 3
1 / -0

In which reaction, there is change in oxidation number of N atom ?

A
$$2NO_2 \rightleftharpoons N_2O_4$$

B
$$2NO_2 + H_2O \rightarrow HNO_3 + HNO_2$$

C
$$NH_4OH \rightarrow NH^+_4 + OH^-$$

D
$$N_2O_5 + H_2O \rightarrow 2HNO_3$$
Question 4
1 / -0

Reaction $$(A) S^{-2} + 4 H_2O_2 \rightarrow SO^{2-}_4 + 4H_2O$$
$$(B)Cl_2 + H_2O_2 \rightarrow 2HCl + O_2$$
The true statement regarding the above reactions is :

A
$$H_2O_2$$ act as reductant in both the reactions.

B
$$H_2O_2$$ acts as oxidant in reaction (A) and reductant in reaction (B).

C
$$H_2O_2$$ acts as an oxidant in reaction in both the reactions.

D
$$H_2O_2$$ acts as reductant in reaction (A) and oxidant in reaction (B).

Solution
Question 5
1 / -0

The brown ring complex compound is formulated as $$[Fe(H_2O)_5NO]SO_4$$. The oxidation state of iron is:

A
+ 1

B
+ 2

C
+ 3

D
+ 6

Solution

Brown ring complex is an iron complex of great significance in inorganic chemistry and salt analysis.
Its formula: $$[Fe(H_2O)_5NO]SO_4$$ (coordination compound)
In this complex, $$NO$$ is in oxidation state of $$+1.$$
So,$$ [Fe(H_2O)_5NO]^{+2}$$ $$SO_4^{-2}$$
$$\overline {x}$$ $$\overline {0}$$ $$\overline {+1}$$
$$x+1=+2$$
$$x=+1$$
Question 6
1 / -0

Oxidation number of oxygen atom in $$O_3$$ molecules is:

A
$$0$$

B
$$-2$$

C
$$+ 2$$

D
$$+1$$

Solution

Its common name is ozone and plays a very important role of protecting earth from harmful UV rays by forming its blanket around earth.
average oxidation state$$=\cfrac {-1+1+0} {3}= 0$$
Question 7
1 / -0

Which of the following is not a redox change ?

A
$$2H_2S + SO_2 \rightarrow 2H_2O + 3S$$

B
$$2BaO + O_2 \rightarrow 2BaO_2$$

C
$$BaO_2 + H_2SO_4 \rightarrow BaSO_4 + H_2O_2$$

D
$$2KClO_3 \rightarrow 2KCl + 3O_2$$

Solution

$$Ba{O}_{2} + {H}_{2}S{O}_{4} \longrightarrow BaS{O}_{4} + {H}_{2}{O}_{2}$$
A redox reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.
$$Ba{O}_{2} + {H}_{2}S{O}_{4} \longrightarrow BaS{O}_{4} + {H}_{2}{O}_{2}$$
As we know that the oxidation no. of oxygen in peroxide is -1.
Since $$Ba{O}_{2}$$ and $${H}_{2}{O}_{2}$$ are peroxides, hence the oxidation number of oxygen in $$Ba{O}_{2}$$ and $${H}_{2}{O}_{2}$$ is -1 as the oxidation no. of oxygen in peroxide is -1.
$$\therefore$$ Oxidation number of barium and hydrogen in $$Ba{O}_{2}$$ and $${H}_{2}{O}_{2}$$ are +2 and +1 respectively.
The oxidation number of barium and hydrogen in $$BaS{O}_{4}$$ and $${H}_{2}S{O}_{4}$$ are +2 and +1 respectively.
The oxidation number of sulphur in $${H}_{2}S{O}_{4}$$ and $$BaS{O}_{4}$$ in same, i.e., +2.
The oxidation number of oxygen in $${H}_{2}S{O}_{4}$$ and $$BaS{O}_{4}$$ in same, i.e., -2.
Since the oxidation state of any atom in the above reaction is not changing, hence the above reaction is not a redox reaction.
Question 8
1 / -0

Which of the following is not a redox reaction ?

A
$$H_2 + Cl_2 \rightarrow 2HCl$$

B
$$NaOH + HCl \rightarrow NaCl + H_2O$$

C
Photosynthesis

D
Cell respiration

Solution
Question 9
1 / -0

Sulphur has highest oxidation state in:

A
$${ H }_{ 2 }S$$

B
$${ { H }_{ 2 }SO }_{ 4 }$$

C
$$Na_{ 2 }{ S }_{ 2 }{ O }_{ 3 }$$

D
$$Na_{2}S_{4}O_{6}$$
Question 10
1 / -0

Heated saw dust catches fire when a drop of concentrated nitric acid is added to it. This is due to

A
dehydration

B
oxidation

C
reduction

D
dehydrogenation

Solution