Question

A compound has $40$% of carbon by weight. If molecular weight of the compound is $90$, the number of carbon atoms present in $1$ molecule of the compound is:

• A. $3$
• B. $2$
• C. $1$
• D. $5$

Answer 1

The correct option is A $3$

$\%C=\frac{\text{Weight of carbon}}{\text{Molecular weight of compound}}\times 100$

$\therefore 40=\frac{w}{90}\times 100$

$\therefore w=36$ g

Mass of 1 atom of $C=12gm$

Number of C atoms $=\frac{36}{12}=3$