Redox Reactions Test

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Redox Reactions Test - 15

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Weekly Quiz Competition

Question 1
1 / -0

Oxidation number of phosphorus in $$Ba(H_{2}PO_{2})_{2}$$ is:

A
$$-3$$

B
$$+1$$

C
$$+3$$

D
$$+5$$

Solution

Let the oxidation state of phosphorus in $$Ba(H_2PO_2)_2$$ be $$x$$.

Then, the sum of all oxidation states should be $$0$$, since, overall charge on the compound is $$0$$.

Therefore, $$+2+4+2x -8=0$$

or, $$x =+1$$

Hence, the oxidation number of phosphorus = $$+1$$.
Question 2
1 / -0

Which of the following is a redox reaction?

A
$$CH_{3}COOH+C_{2}H_{5}OH\rightarrow CH_{3}COOC_{2}H_{5}+H_{2}O$$

B
$$2NaOH+H_{2}SO_{4}\rightarrow Na_{2}SO_{4}+2H_{2}O$$

C
$$Zn+CuSO_{4}\rightarrow ZnSO_{4}+Cu$$

D
$$NaCl+AgNO_{3}\rightarrow AgCl+NaNO_{3}$$

Solution

A reaction in which one reactant undergoes oxidation whereas the other gets reduced during the course of reaction are termed oxidation-reduction reactions or redox reactions.

Oxidation state of $$Zn$$ changes from $$0$$ to $$+2$$(oxidation) while oxidation state of $$Cu$$ changes from $$+2$$ to $$0$$(reduction).

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

When $$Cl^{-}$$ ions are converted to $$Cl_{2}$$ , the oxidation number of chlorine changes from:

A
$$-1$$ to $$0$$

B
$$-1$$ to $$+1$$

C
$$-1$$ to $$+2$$

D
$$-2$$ to $$0$$

Solution

In $$Cl^{-}$$, oxidation number of $$Cl$$ is $$-1$$.

In $$Cl_2$$, oxidation state is zero.

Hence, the oxidation state changes from $$-1$$ to $$0$$.
Question 4
1 / -0

In which of the following compounds, sulphur atom has different oxidation number?

A
$$H_{2}SO_{4}$$

B
$$HSO_{3}^-$$

C
$$SO_{2}Cl_{2}$$

D
$$SO_{3}$$

Solution

The oxidation state of sulphur in $$HSO_3^-$$ is $$+4$$.
In $$H_2SO_4, SO_2Cl_2$$ and $$SO_3$$, the oxidation state of sulfur is $$+6$$ which is the same.
Question 5
1 / -0

Oxidation number of $$Fe$$ in $$Na_2[Fe(CN)_{5}(NO)].2H_{2}O$$ is____________.

A
$$-2$$

B
$$+1$$

C
$$+3$$

D
$$+5$$

Solution

Let $$x$$ be the oxidation number of $$Fe$$.
The oxidation numbers of $$Na^+,\ CN^-$$ ion and $$NO$$ group are $$+1, \:-1$$ and $$0$$ respectively. The sum of the oxidation numbers is zero as the compound is neutral.
Hence, $$2(+1)+x+5(-1)+0 = 0$$ or, $$x = +3$$.
The oxidation state of iron in $$Na_2[Fe(CN)_5(NO)].2H_2O$$ is $$+3$$.
Question 6
1 / -0

The oxidation state of $$N$$ in $$HNO_{3}$$ is:

A
$$+ 7$$

B
$$+10$$

C
$$+5$$

D
$$+3$$

Solution

Let $$x$$ be the oxidation number of $$N$$ in nitric acid.

The oxidation numbers of $$H$$ and $$O$$ in nitric acid are $$+1$$ and $$-2$$ respectively. The sum of the oxidation numbers is zero for the neutral molecule.

Hence, $$1+x+3(-2)=0$$

or, $$x=+5$$

Option C is correct.
Question 7
1 / -0

Oxidation number of sulphur in Caros acid $$(H_{2}SO_{5})$$ is:

A
$$+5$$

B
$$+8$$

C
$$+6$$

D
$$+7$$

Solution

In $$H_2SO_5$$, one peroxide bond is present.
So, the oxidation number of $$2$$ oxygen atoms is $$-2$$. (Compare hydrogen peroxide, $$H_2O_2$$, $$2$$ atoms of oxygen will get $$-1$$ oxidation number each).
The remaining $$3$$ atoms will have $$-2$$ oxidation number each. This is a special case. Oxidation number of each hydrogen atom is $$+1$$ only.
So, finally the oxidation number of sulphur is given by,
$$x -2 -6 +2 = 0$$ (equal to zero as the compound is neutral)
or, $$x= +6$$
The structure of caros acid is as follows:
Question 8
1 / -0

Oxidation number of $$S$$ in $$(CH_{3})_{2}S$$ is

A
$$0$$

B
$$+1$$

C
$$-2$$

D
$$+3$$

Solution

Let $$x$$ be the oxidation number of $$S$$.
The oxidation number of carbon is $$+4$$ and the oxidation number of hydrogen is $$-1$$. The sum of all the oxidation numbers is $$0$$ as the compound is neutral.
Hence, $$2(+4+3(-1))+x=0$$ or, $$x = -2$$.
Thus, the oxidation state of sulphur is $$-2$$.
Question 9
1 / -0

Change in oxidation number is maximum in which of the following reaction?

A
$$Cu + 4HNO_{3}\rightarrow Cu(NO_{3})_{2}+2NO_{2}+2H_{2}O$$

B
$$H_{2}S+4F_{2}\rightarrow 2HF+SF_{6}$$

C
$$Cl_{2}+6KOH\rightarrow 5KCl+KClO_{3}+3H_{2}O$$

D
$$KClO_{3}+H_{2}O+F_{2}\rightarrow KClO_{4}+2HF$$

Solution

In the reaction, $$H_2S+4F_2 \rightarrow 2HF+SF_6$$,

the oxidation state of sulphur changes from $$-2$$ in $$H_2S$$ to $$+6$$ in $$SF_6$$.

Thus, the change in oxidation number is $$8$$. This change is maximum as compared to all the given reactions.

Option B is correct.
Question 10
1 / -0

The oxidation number of manganese in $$ KMnO_{4}$$ is:

A
$$+3$$

B
$$+5$$

C
$$+7$$

D
$$+9$$

Solution

$$KMnO_4$$: Potassium permanganate

Let the oxidation state of $$Mn$$ be $$x$$.

Since the complex is neutral, the sum of all oxidation states will be equal to zero.

Hence, $$+1+x -8=0$$ or, $$x =+7$$

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Redox Reactions Test - 15

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Redox Reactions Test - 15

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SHARING IS CARING

Question 1

$$-3$$

$$+1$$

$$+3$$

$$+5$$

Solution

Question 2

$$CH_{3}COOH+C_{2}H_{5}OH\rightarrow CH_{3}COOC_{2}H_{5}+H_{2}O$$

$$2NaOH+H_{2}SO_{4}\rightarrow Na_{2}SO_{4}+2H_{2}O$$

$$Zn+CuSO_{4}\rightarrow ZnSO_{4}+Cu$$

$$NaCl+AgNO_{3}\rightarrow AgCl+NaNO_{3}$$

Solution

Question 3

$$-1$$ to $$0$$

$$-1$$ to $$+1$$

$$-1$$ to $$+2$$

$$-2$$ to $$0$$

Solution

Question 4

$$H_{2}SO_{4}$$

$$HSO_{3}^-$$

$$SO_{2}Cl_{2}$$

$$SO_{3}$$

Solution

Question 5

$$-2$$

$$+1$$

$$+3$$

$$+5$$

Solution

Question 6

$$+ 7$$

$$+10$$

$$+5$$

$$+3$$

Solution

Question 7

$$+5$$

$$+8$$

$$+6$$

$$+7$$

Solution

Question 8

$$0$$

$$+1$$

$$-2$$

$$+3$$

Solution

Question 9

$$Cu + 4HNO_{3}\rightarrow Cu(NO_{3})_{2}+2NO_{2}+2H_{2}O$$

$$H_{2}S+4F_{2}\rightarrow 2HF+SF_{6}$$

$$Cl_{2}+6KOH\rightarrow 5KCl+KClO_{3}+3H_{2}O$$

$$KClO_{3}+H_{2}O+F_{2}\rightarrow KClO_{4}+2HF$$

Solution

Question 10

$$+3$$

$$+5$$

$$+7$$

$$+9$$

Solution

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