# Oxidation Number Worksheet

An oxidation number of an atom is a positive or negative number which shows how many electrons an atom has gained, lost, or shared to become stable.

Some of the features of Oxidation number are as follows:

1. It is the extent of charge of an atom which is developed in the formation of a compound.

2. It may be positive or negative for an element, E.g. Oxidation number of P in $PH_3 \text{and} PCl_3$ is -3 and +3, respectively.

3. It may be of different value in different compounds for the same element, E.g. Oxidation number of C in $CH_4, CH_3Cl, CH_2Cl_2, CHCl_3 \text{and} CCl_4$ are -4, -2, 0, +2 and +4 respectively.

Questions:

1. In which compound oxygen has +1 oxidation state here:

(a)    $O_3$

(b)   $H_2O_3$

(c)    $OF_2$

(d)   $O_2F_2$

2. Iodine has it’s highest oxidation state in:

(a)    $I_2$

(b)   $KI_3$

(c)    $KIO_4$

(d)   $ICl$

3. Oxidation No. of Mn in $MnC_2O_4$  is:

(a)    +1

(b)   +2

(c)    +3

(d)   +8/3

4. Oxidation No. of C-atom in diamond is:

(a)    Zero

(b)   +4

(c)     -4

(d)    -2

5.  In the reaction $FeSO_4 \overset{KMnO_4}{\underset{H_2SO_4} \rightarrow} Fe_2(SO_4 )_3$ the change of oxidation state of Fe is:

(a)    From +2 to +3

(b)   From +3 to +2

(c)    From +2 to +4

(d)    No change