Question

What is the oxidation state of each individual carbon atom in ${C_2}{O_4}^{2 - }$ ?

Answer 1

To solve the given question, we should have knowledge about oxidation numbers and how to calculate them. Oxidation Number, is the number of electrons gained or lost or shared to form a compound from an element.
Some general rules that follow oxidation number are that the oxidation number of a free element is always $0$, the oxidation number of a Group $1$ element in a compound is $+ 1$ , a Group$2$element in a compound is $+ 2$ and the sum of oxidation numbers of all of the atoms in a compound is of
total charge of the molecule.

Complete answer: Step-1 :

We know that ${C_2}{O_4}^{2 - }$ is an oxalate ion formed from the dissociation of oxalic acid. Oxalic acid has a structure containing $2$ carboxylic acids and carboxylic acid has the same structure. So, both the carbons present in oxalate ions will have the same structure and oxidation state.
Step-2 :
The oxidation state of atoms like Hydrogen, Oxygen and halogens have fixed numbers with some exceptions. The general oxidation state of Oxygen is $+ 2$ with exception of peroxides.
Step-3 :
The overall charge on ion is$- 2$. So, oxidation state of carbon can be calculated as :
$2x - 4(2) = - 2$
$2x = + 6$
$x = + 3$
Therefore, Oxidation state of each carbon atom is $+ 3$ .

Note:
While calculating the oxidation number of an atom in a compound, make sure to determine the charge of the whole compound as it is the most important step while calculating the oxidation number.