Discussion Forum

 Caffeine has a molecular weight of 194 u. If it contains 28.9% by mass of nitrogen, the number of atom of nitrogen in one molecule of caffeine is 

Answer:

Explanation:

 M. wt. of caffeine =194 u

 % of N present in one molecular of caffeine is 28.9% of 

$194 u= \frac{28.9}{100}\times194=56 u$

 Mass of one N atom =14 m

 =1N atom (  $\because$ 14 m=14 u)

$\therefore$     $56 u=\frac{56}{14}$  N atom =4 N atom