Question

An organic compound was synthesized and found to contain only c, h, n, o, and cl. it was observed that when a 0.150 g sample of the compound was burned, it produced 0.138 g of co2 and 0.0566 g of h2o. all the nitrogen in a different 0.200 g sample of the compound was converted to nh3, which was had a mass of 0.0238 g. finally, the chlorine in a 0.125 g sample of the compound was converted to agcl. the agcl, when dried, weighed 0.251 g. determine the percent mass of each of these elements.

Answer 1

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 %     =   11       %

                                           TOTAL = 100      %