Question

What is the oxidation number and valency of carbon in methanal $\left(HCHO\right)$?

• A. 0, 4
• B. 1,4
• C. 0,2
• D. None of these

Answer 1

Answer: (A)

0, 4

For compounds containing C atoms, the oxidation number of C atom $=\frac{2n_O-n_H}{n_C}$
Here, $n_O,n_{H}and{n}_C$ represents the number of oxygen, hydrogen and carbon atoms respectively.
For methanal $C{H}_{2}O$, the oxidation number of C atom $=\frac{2n_O-n_H}{n_C}=\frac{2\times 1-2}{1}=0$
The valency of C in methanal is 4 as it is attached to 2 H atoms by two single bonds and one oxygen atom by a double bond.
$H-\stackrel{\stackrel{O}{||}}{C}-H$