Calculation of number of nitrogen atoms in one molecule of caffeine

To calculate the number of nitrogen atoms in one molecule of caffeine, we need to use the following information:

- Molecular mass of caffeine = 194
- Percentage of nitrogen by mass in caffeine = 28.9%

Step 1: Convert percentage of nitrogen to mass of nitrogen

To do this, we assume that we have 100 g of caffeine. Then, the mass of nitrogen in 100 g of caffeine is:

Mass of nitrogen = Percentage of nitrogen by mass x Mass of caffeine / 100
= 28.9 x 100 / 1000 (since the molecular mass of caffeine is 194 g/mol)
= 2.809 g

Step 2: Calculate the number of moles of nitrogen

To do this, we need to use the atomic mass of nitrogen, which is 14 g/mol. The number of moles of nitrogen in 2.809 g is:

Number of moles of nitrogen = Mass of nitrogen / Atomic mass of nitrogen
= 2.809 / 14
= 0.201 moles

Step 3: Calculate the number of nitrogen atoms

To do this, we need to use Avogadro's number, which is 6.022 x 10^23 atoms/mol. The number of nitrogen atoms in 0.201 moles is:

Number of nitrogen atoms = Number of moles of nitrogen x Avogadro's number
= 0.201 x 6.022 x 10^23
= 1.209 x 10^23

Therefore, the number of nitrogen atoms in one molecule of caffeine is 1.209 x 10^23.

Explanation:
The given problem can be solved using basic concepts of stoichiometry, which involves the calculation of the number of moles of a substance based on its mass and molar mass. Then, using Avogadro's number, we can convert the number of moles to the number of atoms. The final answer gives the number of nitrogen atoms in one molecule of caffeine.

Calculate 28.9% of 194 it will the mass of nitrogen atom in one mole of caffeine its coming 56.06 approx 56 mass of one atom of nitrogen=14 mass of 4 atoms =56 so ans is 4