Aspirin (C_9H_8O_4) is produced from salicylic acid (C_7H_6O_3) and acetic anhyd

Question

Aspirin (C_9H_8O_4) is produced from salicylic acid (C_7H_6O_3) and acetic anhydride (C_4H_6O_3): C_7H_6O_3 + C_4H_6O_3 rightarrow C_9H_8O_4 + HC_2H_3O_2 How much salicylic acid is required to produce 1.5. 10^2 kg of aspirin, assuming that all ofthe salicylic acid is converted to aspirin? How much salicylic acid would be required if only 80% of the salicylic acid is converted to aspirin? What is the theoretical yield of aspirin if 185 kg of salicylic acid is allowed to react with 125 kg of acetic anhydride? If the situation described in part (c) produces 182 kg of aspirin, what is the percentage yield? are the ions present upon dissolving each of the following in water:

Explanation / Answer

Answer – We are given, reaction –

C7H6O3 + C4H6O3 ----> C9H8O4 + HC2H3O2

a) Mass of C9H8O4 = 1.5*102 kg = 150 g

moles of C9H8O4 = 150 g /180.16 g.mol-1

                           = 0.833 moles

From the balanced reaction –

1 mole of C9H8O4 = 1 moles of C7H6O3

So, 0.833 moles of C9H8O4 = ?

= 0.833 moles of C7H6O3

So, mass of C7H6O3 = 0.833 moles * 138.123 g/mol

                                  =115 g

b) From the above calculation we calculated for the 100 % conversion, so if there is only 80 % conversion then

mass of salicylic acid = 80 % * 115 g / 100 %

                                    = 92 g

c) Mass of salicylic acid = 185 kg = 185000 g , mass of acetic anhydride = 125 kg = 125000 g

First we need to calculate the moles of each reactant

Moles of C7H6O3 = 185000 g / 138.123 g.mol-1

                                            = 1339.4 moles

Moles of C4H6O3 = 125000 g / 102.09 g.mol-1

                               = 1224.41 moles

Moles of C9H8O4 from the C7H6O3

From the balanced reaction –

All has mole ratio 1:1 in the balanced reaction, so

Moles of C7H6O3 = moles of C9H8O4 = 1339.4 moles

From the C4H6O3

moles of C4H6O3 = moles of C9H8O4 =1224.41 moles

so, moles of C9H8O4 is lowest from the acetic anhydride, so limiting reactant is acetic anhydride and

moles of aspirin C9H8O4 = 1224.41 moles

Theoretical yield of aspirin C9H8O4 = 1224.41 moles * 180.16 g/mol

                                                          = 220590 g

                                                          = 220.6 kg

d) Actual yield of aspirin C9H8O4 = 182 kg and we calculated theoretical yield = 220.6 kg

so, percent yield = actual yield / theoretical yield *100 %

                           = 182 kg / 220.6 kg*100 %

                          = 82.5 %

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