The composition is 25.1 % C, 4.22 % H, 9.79 % N, 49.7 % Cl, 11 % O.
We must calculate the masses of C, H, N, Cl, and O from the masses given.
Mass of C in 150 mg X =138 mg CO₂ × (12.01 mg C/44.01 mg CO₂) = 37.66 mg C
Mass of H in 150 mg X = 56.6 mg H₂O × (2.016 mg H/18.02 mg H₂O) = 6.332 mg H
Mass of N in 200 mg X = 23.8 mg NH₃ × (14.01 g N/17.03 g NH₃) = 19.58 mg N
Mass of N in 150 mg X = 19.58 mg N × (150 mg X/200 mg X) = 14.68 mg N
Mass of Cl in 125 mg X = 251 mg AgCl × (35.45 mg Cl/143.32 mg AgCl) = 62.08 mg Cl
Mass of Cl in 150 mg X = 62.08 mg Cl × 150 mg /125 mg X) = 74.50 mg Cl
Mass of O in 150 mg X = (150 – 37.66 -6.332 -14.68 – 74.50) mg = 16.8 mg
% C = 37.66 mg/150 mg × 100 % = 25.1 %
% H = 6.332 mg/150 mg × 100 % = 4.22 %
% N = 19.58 mg/200 mg × 100 % = 9.79 %
% Cl = 62.08 mg/125 mg × 100 % = 49.7 %
% O = 16.8 mg/150 mg × 100 % = <u>11 %</u>
TOTAL = 100 %