Caffeine has a molecular weight of 194. If it contains 28.9% by mass of nitrogen, number of atoms of nitrogen in one molecule of caffeine is?
Hello Jaswin,
The answer to this problem lies in the simple unitary method followed by a division.
Considering 100g of caffeine, the content of nitrogen is 28.9g.
Now, 100g of caffeine contains 28.9g of Nitrogen
1g of caffeine contains 28.9/100 g of Nitrogen
therefore 194g of caffeine contains (28.9/100)*194 = 56.06g of Nitrogen.
Dividing the weight of Nitrogen present with the atomic weight of Nitrogen, i.e 14, 56.06/14, we get approximately 4.
Therefore 4 atoms of Nitrogen is present in 194g of caffeine.