The equivalent weight of carbon in ${\mathrm{CO}}_2 \mathrm{is}$

In ${\mathrm{CO}}_2$ the valency of C is 4 because it forms two double bonds with oxygen atom (total 4 bonds).

Equivalent weight of carbon , (C ) $=\frac{\mathrm{Atomic} \mathrm{weight} \mathrm{of} \mathrm{C}}{\mathrm{valency} \mathrm{of} \mathrm{C}}$

$=\frac{12}{4}=3$