Question

what is the mass percent of carbon, hydrogen, nitrogen, and oxygen in caffeine, C8H10N4O2.

Answer 1

M(C₈H₁₀N₄O₂)=194.193 g/mol

w(C)=8A(C)/M(C₈H₁₀N₄O₂)
w(H)=10A(H)/M(C₈H₁₀N₄O₂)
w(N)=4A(N)/(C₈H₁₀N₄O₂)
w(O)=1-{w(C)+w(H)+w(N)}

w(C)=8·12.011/194.193=0.4948
w(H)=10·1.008/194.193=0.0519
w(N)=4·14.007/194.193=0.2885
w(O)=0.1648