Mass of 1 mole of N = 14 u
1 mole contains 6.023 x 1023 atoms
Hence mass of 1 atom = 14/ 6.023 x 1023 = 2.32 x 10−23u
Molar mass of caffeine is 194. If it contains 28.9% of nitrogen by mass, calculate the number of nitrogen atoms in one molecule of caffeine .