Question

What is the sum of oxidation numbers of all the carbon atoms except that attached to $-CHO$ group in $C_6{H}_{5}CHO$?

• A. $-6$
• B. $-5$
• C. $-4$
• D. $-2$

Answer 1

Answer: (C)

$-4$

Here answer is option $C$

When there is $C-C$ bond ox. no. of $C$ counted as 0

When there is $C-H$ bond ox. no. of $C$ counted as -1, since $C$ is more electronegative than $H$

When there is $C-O$ bond ox. no. of $C$ counted as +2, since C$islesselectronegativethan$O$

Using the formula calculating the oxidation state of a single atom of carbon;

$6x+5+x+1+(-2)=0x=-\frac{4}{7}$

Since sum of oxidation state of all $C$ atoms(7 in number)

$-\frac{4}{7}\times 7=-4$