O.N. of C in $C_3O_2$ is:

Question

Accepted Answer

The correct option is (4):
The compound $C\_3O\_2$ is carbon suboxide. To determine the average oxidation number of carbon in $C\_3O\_2$, we assign the standard oxidation number of oxygen as -2. Since there are two oxygen atoms, their total contribution to the oxidation number is $2 \times (-2) = -4$. The sum of the oxidation numbers in a neutral compound must be zero. Therefore, if we let 'x' be the average oxidation number of carbon, we have $3x + (-4) = 0$. Solving for x, we get $3x = 4$, so $x = 4/3$. It's important to note that this is an average oxidation number, as the carbons in carbon suboxide have different oxidation states due to its linear structure (O=C=C=C=O). The two terminal carbon atoms have an oxidation state of +2, while the central carbon atom has an oxidation state of 0. $(+2 + 0 + +2)/3 = 4/3$.

The incorrect option is (1): 3/3. An average oxidation number of 1 for carbon would imply a different molecular structure or bonding, which is not consistent with carbon suboxide. For instance, if each carbon had an oxidation number of +1, the total for carbon would be +3, leaving the molecule with a net charge of -1 (3(+1) + 2(-2) = -1), which contradicts the neutrality of $C_3O_2$.

The incorrect option is (2): 3/2. An average oxidation number of 1.5 for carbon would similarly lead to an incorrect overall charge for the molecule. If carbon's average oxidation state were +1.5, then $3 	imes (+1.5) = +4.5$, which when combined with the oxygen's total of -4, would result in a net charge of +0.5, again violating the compound's neutrality.

The incorrect option is (3): 3/4. This option suggests an average oxidation number of 0.75 for carbon. If this were the case, the total positive charge from the carbon atoms would be $3 	imes (+0.75) = +2.25$. When combined with the -4 from oxygen, this would result in a net charge of -1.75, which is incorrect for a neutral molecule.