Caffeine has the molecular formula C8H10N4O2. To determine the percentage composition of carbon, hydrogen, and nitrogen, we first need to calculate the molar mass of caffeine and the molar mass of each element in the compound.Molar mass of caffeine:Carbon C = 8 atoms 12.01 g/mol = 96.08 g/molHydrogen H = 10 atoms 1.01 g/mol = 10.10 g/molNitrogen N = 4 atoms 14.01 g/mol = 56.04 g/molOxygen O = 2 atoms 16.00 g/mol = 32.00 g/molTotal molar mass of caffeine = 96.08 + 10.10 + 56.04 + 32.00 = 194.22 g/molNow, we can calculate the percentage composition of each element:Percentage of Carbon C : 96.08 g/mol C / 194.22 g/mol caffeine 100% = 49.48%Percentage of Hydrogen H : 10.10 g/mol H / 194.22 g/mol caffeine 100% = 5.20%Percentage of Nitrogen N : 56.04 g/mol N / 194.22 g/mol caffeine 100% = 28.85%So, the percentage composition of caffeine is approximately 49.48% carbon, 5.20% hydrogen, and 28.85% nitrogen.