Redox Reactions Test

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Redox Reactions Test - 26

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Weekly Quiz Competition

Question 1
1 / -0

Determine the oxidation number of underlined atoms in following :

$$8K\underline{Cl}O_3 + 24HCl \rightarrow + 8K\underline {Cl}+ 12 H_2O + 9\underline{Cl}_2+ 6\underline{Cl}O_2$$

A
$$+5,\: -1,\: 0,\: +4$$

B
$$+5,\: -1,\: 0,\: +2$$

C
$$+4,\: -1,\: 0,\: +5$$

D
None of these

Solution

Let X be the oxidation number of Cl in $$K{Cl}O_3$$
$$\displaystyle 1+X+3(-2) = 0 $$
$$\displaystyle X = +5 $$

Let X be the oxidation number of Cl in $$K{Cl}$$
$$\displaystyle 1+X = 0 $$
$$\displaystyle X= -1 $$

Let X be the oxidation number of Cl in $$ {Cl}_2$$
$$\displaystyle 2X=0 $$
$$\displaystyle X=0 $$

Let X be the oxidation number of Cl in $$ {Cl}O_2$$
$$\displaystyle X+2(-2) = 0 $$
$$\displaystyle X = +4 $$

The oxidation number of underlined atoms in $$8K\underline{Cl}O_3 + 24HCl \rightarrow + 8K\underline {Cl}+ 12 H_2O + 9\underline{Cl}_2+ 6\underline{Cl}O_2$$ are $$+5,\: -1,\: 0,\: +4$$ respectively.
Question 2
1 / -0

The oxidation number of iodine in each of the following compounds, $$I{F}_{7}, I{F}_{5}, KI, {I}_{2}, ICI$$ and $$HI{O}_{4}$$ respectively, is :

A
$$+7,\: +5,\: -1,\: 0,\: +1,\: +7$$

B
$$+7,\: +5,\: -1,\: 0,\: +2,\: +7$$

C
$$+7,\: +5,\: -1,\: 0,\: +4,\: +7$$

D
none of these

Solution

Let $$x$$ be the oxidation number of iodine.
Since, the overall charge on the complex is $$0$$, the sum of oxidation states of all elements in it should be equal to $$0$$.
$$I{F}_{7}$$; $$x+7(-1)=0; \:x=+7$$

$$ I{F}_{5}$$; $$x+5(-1)=0;\: x=+5$$

$$KI$$; $$1+x=0;\: x= -1$$

$${I}_{2}$$; $$2x=0; \:x=0$$

$$ ICI$$; $$x-1=0; x= \:+1$$

$$ HI{O}_{4}$$; $$1+x+4(-2)=0;\: x= +7$$
The oxidation number of iodine in $$I{F}_{7},\ I{F}_{5},\ KI, {I}_{2},\ ICI$$ and $$HI{O}_{4}$$ is $$+7,\ +5,\ -1,\ 0,\ +1$$ and $$+7$$ respectively.
Question 3
1 / -0

What is the oxidation number and valency of carbon in methanal $$\left(HCHO\right)$$?

A
0, 4

B
1,4

C
0,2

D
None of these

Solution

For compounds containing C atoms, the oxidation number of C atom $$= \frac {2n_O-n_H}{n_C}$$
Here, $$n_O, n_H and n_C$$ represents the number of oxygen, hydrogen and carbon atoms respectively.
For methanal $$ CH_2O$$, the oxidation number of C atom $$\displaystyle = \frac {2n_O-n_H}{n_C}=\frac {2 \times 1-2}{1}=0$$
The valency of C in methanal is 4 as it is attached to 2 H atoms by two single bonds and one oxygen atom by a double bond.
$$\displaystyle H- \overset {\overset {\displaystyle O}{||}}{C}-H$$
Question 4
1 / -0

Assign oxidation numbers to the elements in the following ionic compounds.
a. $$NaBr$$ b. $$MgO$$ c. $$Al{F}_{3}$$

A
a. Na = $$+1$$, Br = $$-1$$; b. Mg = $$+2$$, O = $$-2$$; c. Al = $$+3$$, F = $$-1$$

B
a. Na = $$+2$$, Br = $$-2$$; b. Mg = $$+2$$, O = $$-2$$; c. Al = $$+3$$, F = $$-1$$

C
a. Na= $$+1$$, Br = $$-1$$; b. Mg = $$+1$$, O = $$-1$$; c. Al = $$+3$$, F = $$-1$$

D
None of these

Solution

In sodium bromide ($$NaBr$$), the oxidation number of Na is $$+1$$ and that of Br is $$-1$$.
In magnesium oxide ($$MgO$$), the oxidation number of Mg is $$+2$$ and that of O is $$-2$$.
In Aluminium fluoride ($$AlF_3$$), the oxidation number of Al is $$+3$$ and that of F is $$-1$$.
Question 5
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Directions For Questions

The valency of carbon is generally $$4$$ but its oxidation state may be $$-4,\: -2,\: 0,\: +2,\: -1$$ etc. In the compounds containing $$C, H$$ and $$O$$, the oxidation number of $$C$$ is calculated as:
Oxidation number of $$C = \displaystyle\frac { 2{ n }_{ O }-{ n }_{ H } }{ { n }_{ C } }$$
where, $${ n }_{ O }, { n }_{ H }$$ and $${ n }_{ C }$$ are the number of oxygen, hydrogen and carbon atoms respectively.

...view full instructions

The oxidation state of $$C$$ in diamond is :

A
$$0$$

B
$$+1$$

C
$$-1$$

D
$$+2$$

Solution

Carbon in diamond is in elemental state, so the oxidation state of $$C$$ in diamond is zero.
The structure of diamond has been shown below:
Question 6
1 / -0

Which of the following statement is not correct?

A
The oxidation number of $$S$$ in $${ \left( N{ H }_{ 4 } \right) }_{ 2 }{ S }_{ 2 }{ O }_{ 8 }$$ is $$+6$$

B
The oxidation number of $$Os$$ in $$Os{ O }_{ 4 }$$ is $$+8$$

C
The oxidation number of $$S$$ in $${ H }_{ 2 }S{ O }_{ 5 }$$ is $$+8$$

D
The oxidation number of $$O$$ in $$K{ O }_{ 2 }$$ is $$-\frac { 1 }{ 2 }$$

Solution

A. $${ \left( \overset { +1 }{ { NH }_{ 4 } } \right) }_{ 2 }{ S }_{ 2 }{ O }_{ 8 }^{ 2- }$$
$$\therefore $$ Oxidation state of $$S = +6$$. Since, $${ S }_{ 2 }{ O }_{ 8 }^{ 2- }$$ has one peroxide bond.
B. Oxidation state of $$Os$$ in $$OsO_4$$ is $$ +8$$.
C. Oxidation state of $$S$$ in $${ H }_{ 2 }S{ O }_{ 5 }=+6$$ (Since it has one peroxide bond).
D. $${ K }^{ 1+ }{ O }_{ 2 }^{ 1- }$$, oxidation state of $$O= - \dfrac{ 1 }{ 2 }$$.
Hence, only option C is incorrect.
Question 7
1 / -0

Calculate the oxidation number of the underlined elements.
a. $$\underline { P } { H }_{ 3 }$$ b. $$\underline { S } { O }_{ 2 }$$ c. $$H\underline { N } { O }_{ 3 }$$ d. $${ H }_{ 3 }\underline { P } { O }_{ 4 }$$

A
a. $$-3$$; b. $$+4$$; c. $$+5 $$; d. $$+5$$

B
a. $$-3 $$; b. $$+2$$; c. $$+5 $$; d. $$+5$$

C
a. $$-3 $$; b. $$+4$$; c. $$+5$$; d. $$+4$$

D
None of these

Solution

a) Let $$x$$ be the oxidation number of P in phosphine $$PH_3$$.
Since, the overall charge on the complex is $$0$$, the sum of oxidation states of all elements in it should be equal to $$0$$.
$$x+3(+1)=0$$
$$x=+3$$.
Similarly,
b) Let $$x$$ be the oxidation number of S in sulphur dioxide $$SO_2$$.
$$x+2(-2)=0$$
$$x=+4$$.
c) Let $$x$$ be the oxidation number of N in nitric acid $$HNO_3$$.
$$1+x+3(-2)=0$$
$$x=+5$$.
Let $$x$$ be the oxidation number of P in phosphoric acid $$H_3PO_4$$.
$$3(+1)+x+4(+1)=0$$
$$x=+5$$.
Question 8
1 / -0

What is the oxidation number of $$Mg$$ and $$N$$ in magnesium nitride?

A
$$Mg = +2; N = -3$$

B
$$Mg = +1; N = -3$$

C
$$Mg = +2; N = -2$$

D
None of these

Solution

In magnesium nitride ($$Mg_3N_2$$), the oxidation number of Mg and N are $$+2$$ and $$-3$$ respectively.
Question 9
1 / -0

Calculate the oxidation number of the underlined elements in the following compounds.
a. $$K\underline { Mn } { O }_{ 4 }$$ b. $$\underline { Cr } { O }_{ 2 }{ Cl }_{ 2 }$$ c. $$Na\underline { I } { O }_{ 3 }$$

A
a. $$+7$$ b. $$+6$$ c. $$+5$$

B
a. $$+9 $$ b. $$+6$$ c. $$+5$$

C
a. $$+7$$ b. $$0$$ c. $$+5$$

D
None of these

Solution

a) Let $$x$$ be the oxidation number of Mn in potassium permanganate $$KMnO_4$$.
Since, the overall charge on the complex is $$0$$, the sum of oxidation states of all elements in it should be equal to $$0$$.
$$+1+x+4(-2)=0$$
$$x=+7$$
b) Let $$x$$ be the oxidation number of Cr in chromyl chloride $$CrO_2Cl_2$$.
$$x+2(-2)+2(-1)=0$$
$$x=+6$$
c) Let $$x$$ be the oxidation number of I in nitric acid $$NaIO_3$$.
$$1+x+3(-2)=0$$
$$x=+5$$
Question 10
1 / -0

The oxidation number of $$P$$ in $${ Na}_{4 }{ P }_{ 2 }{ O }_{ 7 }$$ is:

A
$$+3$$

B
$$+2$$

C
$$+5$$

D
$$-3$$

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Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 26

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Redox Reactions Test - 26

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Question 1

$$+5,\: -1,\: 0,\: +4$$

$$+5,\: -1,\: 0,\: +2$$

$$+4,\: -1,\: 0,\: +5$$

None of these

Solution

Question 2

$$+7,\: +5,\: -1,\: 0,\: +1,\: +7$$

$$+7,\: +5,\: -1,\: 0,\: +2,\: +7$$

$$+7,\: +5,\: -1,\: 0,\: +4,\: +7$$

none of these

Solution

Question 3

0, 4

1,4

0,2

None of these

Solution

Question 4

a. Na = $$+1$$, Br = $$-1$$; b. Mg = $$+2$$, O = $$-2$$; c. Al = $$+3$$, F = $$-1$$

a. Na = $$+2$$, Br = $$-2$$; b. Mg = $$+2$$, O = $$-2$$; c. Al = $$+3$$, F = $$-1$$

a. Na= $$+1$$, Br = $$-1$$; b. Mg = $$+1$$, O = $$-1$$; c. Al = $$+3$$, F = $$-1$$

None of these

Solution

Question 5

$$0$$

$$+1$$

$$-1$$

$$+2$$

Solution

Question 6

The oxidation number of $$S$$ in $${ \left( N{ H }_{ 4 } \right) }_{ 2 }{ S }_{ 2 }{ O }_{ 8 }$$ is $$+6$$

The oxidation number of $$Os$$ in $$Os{ O }_{ 4 }$$ is $$+8$$

The oxidation number of $$S$$ in $${ H }_{ 2 }S{ O }_{ 5 }$$ is $$+8$$

The oxidation number of $$O$$ in $$K{ O }_{ 2 }$$ is $$-\frac { 1 }{ 2 }$$

Solution

Question 7

a. $$-3$$; b. $$+4$$; c. $$+5 $$; d. $$+5$$

a. $$-3 $$; b. $$+2$$; c. $$+5 $$; d. $$+5$$

a. $$-3 $$; b. $$+4$$; c. $$+5$$; d. $$+4$$

None of these

Solution

Question 8

$$Mg = +2; N = -3$$

$$Mg = +1; N = -3$$

$$Mg = +2; N = -2$$

None of these

Solution

Question 9

a. $$+7$$ b. $$+6$$ c. $$+5$$

a. $$+9 $$ b. $$+6$$ c. $$+5$$

a. $$+7$$ b. $$0$$ c. $$+5$$

None of these

Solution

Question 10

$$+3$$

$$+2$$

$$+5$$

$$-3$$

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