Caffeine has the molecular formula C8H10N4O2. To determine the percentage composition of carbon C , hydrogen H , and nitrogen N , we first need to find the molar mass of each element and the molar mass of caffeine.Molar mass of C: 12.01 g/molMolar mass of H: 1.01 g/molMolar mass of N: 14.01 g/molMolar mass of O: 16.00 g/molNow, let's calculate the molar mass of caffeine:Caffeine molar mass = 8 12.01 + 10 1.01 + 4 14.01 + 2 16.00 Caffeine molar mass = 96.08 + 10.10 + 56.04 + 32.00Caffeine molar mass = 194.22 g/molNext, we'll find the percentage composition of each element:Percentage of C = Total mass of C in caffeine / Molar mass of caffeine 100Percentage of C = 96.08 g / 194.22 g 100Percentage of C 49.48%Percentage of H = Total mass of H in caffeine / Molar mass of caffeine 100Percentage of H = 10.10 g / 194.22 g 100Percentage of H 5.20%Percentage of N = Total mass of N in caffeine / Molar mass of caffeine 100Percentage of N = 56.04 g / 194.22 g 100Percentage of N 28.85%So, the percentage composition of carbon, hydrogen, and nitrogen in a sample of caffeine is approximately 49.48% carbon, 5.20% hydrogen, and 28.85% nitrogen.