Question

Oxidation state of ${\text{Cr}}$ in ${\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}$

Answer 1

Hint: Oxidation state is the number of electrons that the atom of an element loses or gains during chemical bond formation. The oxidation number can be zero, negative, or positive. Use the oxidation number rules to calculate the oxidation state of carbon.

Step by step answer: The formula of a compound given to us is${\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}$. Here combining atoms are chromium, oxygen and chlorine. It is a neutral compound as there is no charge on it.

-Calculate the oxidation state of chromium using the oxidation number rules as follows:
As per the oxidation number rules, the oxidation number of oxygen is always -2 except in peroxide. In peroxide oxidation the number of oxygen is -1.
So, for given compound ${\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}$oxidation number of oxygen is -2
As per the rules, the oxidation number of chlorine is -1.
Now, calculate the oxidation number of chromium as follows:
(Number of chromium atom) (Oxidation number of chromium) + (Number of oxygen atom) (Oxidation number of oxygen) + (Number of chlorine atom)(oxidation number of chlorine atom)= 0
In the formula of ${\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}$ there is 1 chromium atom, 2 oxygen atoms and 2 chlorine atoms.
Thus,
(1) (Oxidation state of chromium) + (2) (-2) + (2) (-1) = 0
The oxidation state of carbon = +6
Hence, the oxidation number of chromium in ${\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}$ is +6.

Note: Oxidation state is the only apparent charge which represents the positive or negative character of the atom. It is necessary to denote the charge of the oxidation state even if it is positive. Oxidation is the loss of electrons while reduction is the gain of electrons. During oxidation, the oxidation number of an atom increases while during the reduction, the oxidation number of an atom decreases.