Question

An organic compound made of $C,H$ and $N$ contains $20$% nitrogen. Its minimum molecular weight is:

• A. $70$
• B. $140$
• C. $100$
• D. $65$

Answer 1

The correct option is A $70$

Let the molecular weight be $X$. Then $20$% of $X$ is equal to molecular weight of Nitrogen ($N$).

$20$% of $X$ = $14$

$X$/$5$ = $14$

Therefore the minimun molecular weight is $14\times 5$ = $70$.