Aspirin, C9H8O4, is produced from salicylic acid, C7H6O3, and acetic anhydride,

Question

Aspirin, C9H8O4, is produced from salicylic acid, C7H6O3, and acetic anhydride, C4H6O3, as shown below. C7H6O3 + C4H6O3 C9H8O4 + HC2H3O2 (a) How much salicylic acid is required to produce 5.0x10^2 kg of aspirin, assuming that all of the salicylic acid is converted to aspirin? (b) How much salicylic acid would be required if only 85% of the salicylic acid is converted to aspirin? (c) What is the theoretical yield of aspirin if 157 kg of salicylic acid is allowed to react with 127 kg of acetic anhydride? (d) If the situation described in part (c) produces 167 kg of aspirin, what is the percentage yield?

Explanation / Answer

C7H6O3 + C4H6O3 --> C9H8O4 + HC2H3O2

a)

SA requre for

Aspirin = 5*10^2 kg = 5*10^5 grams

MW of Aspriin = 180.157 g/mol

mol = mass/MW = (5*10^5)/180.157 = 2775.357 mol of Aspriin

then

since ratio si 1:1

we need

2775.357 of salicylic acid

MW of SA = 138.121 g/mol

mass = mol*MW = 138.121 *2775.357 = 383335.084197 g of salicylic acid are required, or 383.34 kg of S.Acid

b)

if we only convert 85% of S.A

then

for 100% = 383.34

then for 85% = x?

x = 383.34 *100/85 = 450.988 kg of S. Acid needed for incomplete 85%

c)

yield if 157 kg of S.A react with 127 kg of Ac.Andh

change to kmol

MWof SA = 138.121

kmol = 157 /138.121 = 1.13668

for Ac.Ah

MW = 102.09

kmol = 127/102.09 = 1.24400

the ratio is 1:1 so

1.13668 kmol of S.Acid will produce 1.13668 kmol of aspirin

the yield (theoretical) will be = 1.13668 kmol or 1136.68 mol of Aspirin

mass of aspirin = mol*MW = 180*1.13668 = 204.6024 kg of Aspirin

d)

if actual yield is 167 kg of aspirin

% yield = real/theoretical * 100 = 167 /204.6024 * 100 = 81.621720%

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