Caffeine has the molecular formula C8H10N4O2. To determine the percent composition of carbon, hydrogen, and nitrogen, we need to find the molar mass of each element in the compound and then divide it by the molar mass of the entire compound.First, let's find the molar mass of each element in 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/molNow, let's find the molar mass of the entire compound:Molar mass of caffeine = 96.08 g/mol C + 10.10 g/mol H + 56.04 g/mol N + 32.00 g/mol O = 194.22 g/molNext, we'll find the percent composition of each element:Percent composition of Carbon C = 96.08 g/mol 194.22 g/mol 100 = 49.48%Percent composition of Hydrogen H = 10.10 g/mol 194.22 g/mol 100 = 5.20%Percent composition of Nitrogen N = 56.04 g/mol 194.22 g/mol 100 = 28.85%So, the percent composition of caffeine is approximately 49.48% carbon, 5.20% hydrogen, and 28.85% nitrogen.