Aspirin (C 9 H 8 O 4 ) is producedfrom salicylic acid (C 7 H 6 O 3 ), andacetic

Question

Aspirin (C9H8O4) is producedfrom salicylic acid (C7H6O3), andacetic anhydride (C4H6O3), asshown below. C7H6O3 +C4H6O3 -->C9H8O4 +HC2H3O2 (a) How much salicylic acid is required to produce 3.7 x102 kg of aspirin, assuming that all of the salicylicacid is converted to aspirin? _____ kg (b) How much salicylic acid would be required if only 53% ofthe salicylic acid is converted to aspirin? _____ kg (c) What is the theoretical yield of aspirin if 163 kg ofsalicylic acid is allowed to react with 131 kg of aceticanhydride? _____ kg (d) If the situation described in part (c) produces 155 kg ofaspirin, what is the percentage yield? _____% Aspirin (C9H8O4) is producedfrom salicylic acid (C7H6O3), andacetic anhydride (C4H6O3), asshown below. C7H6O3 +C4H6O3 -->C9H8O4 +HC2H3O2 (a) How much salicylic acid is required to produce 3.7 x102 kg of aspirin, assuming that all of the salicylicacid is converted to aspirin? _____ kg (b) How much salicylic acid would be required if only 53% ofthe salicylic acid is converted to aspirin? _____ kg (c) What is the theoretical yield of aspirin if 163 kg ofsalicylic acid is allowed to react with 131 kg of aceticanhydride? _____ kg (d) If the situation described in part (c) produces 155 kg ofaspirin, what is the percentage yield? _____% (a) How much salicylic acid is required to produce 3.7 x102 kg of aspirin, assuming that all of the salicylicacid is converted to aspirin? _____ kg (b) How much salicylic acid would be required if only 53% ofthe salicylic acid is converted to aspirin? _____ kg (c) What is the theoretical yield of aspirin if 163 kg ofsalicylic acid is allowed to react with 131 kg of aceticanhydride? _____ kg (d) If the situation described in part (c) produces 155 kg ofaspirin, what is the percentage yield? _____%

Explanation / Answer

(A) Calculate the moles (n) of aspirin that corresponds to the weightgiven; then use the fact that salicylic acid (SA) produces aspirinin a 1:1 ratio (as per the equation, which is balanced) tocalculate the moles, and then the mass, of salicylic acid required.Watch the units.     n(aspirin) = mass / molar mass     = 370 kg / 0.180kg/mol                   = 2055.56 mol          n(SA) =n(aspirin)     n(SA) = 2055.56 mol    mass(SA) = n * molar mass                   = 2055.56 mol * 0.138 kg/mol                   = 284 kg (B) The ratio of aspirin to SA is now 0.53 : 1. Thus the actual molesof SA required is greater.     0.53 * n(SA) = n(aspirin) You could work through the whole calculation again or just cutstraight to:     mass(SA) = 284 kg / 0.53                  = 535kg (C) Calculate the moles of each reagent to see which is limiting.      n(SA) = 163 kg / 0.138 kg/mol               = 1181 mol     n(AA) = 131 kg / 0.102 kg/mol               = 1284 mol So SA is limiting, and we can calculate the theoretical yield,assuming 100% reaction efficiency, as:     n(aspirin) = n(SA) = 1181 mol     mass(aspirin) = 1181 mol * 0.180 kg/mol = 213kg (D)     % Yield = Actual Yield / Theoretical Yield *100%                 = 155 / 213 * 100                 = 73%

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