Answer to Question #254533 in Chemistry for Katerina

Question

Aspirin (acetylsalicylic acid) is widely used to treat pain, fever, and inflammation. In COVID 19 treatment it is also given as a blood thinner to prevent blood clotting for patients showing very high D-dimer value.

It is produced from the reaction of salicylic acid with acetic anhydride with sulphuric acid as a protonating agent.

In an industry, 10.00 kg of salicylic acid is mixed with 10.00 kg of acetic anhydride.

a) Which reactant is limiting? Which is in excess?

b) What mass of excess reactant is left over?

c) What mass of aspirin is formed assuming 100% yield (Theoretical yield)?

d) What mass of aspirin is formed if the reaction yield is 70.0%?

Answer 1

11C₇H₆O₃ + C₄H₆O₃ = 9C₉H₈O₄

According to the reaction, n (C₇H₆O₃) = 11 x n (C₄H₆O₃)

n = m / M

M (C₇H₆O₃) = 138.121 g/mol

M (C₄H₆O₃) = 102.09 g/mol

M (C₉H₈O₄) = 180.16 g/mol

n (C₇H₆O) = 10 000 / 138.121 = 72.4 mol

n (C₄H₆O₃) = 10 000 / 102.09 = 97.95 mol

a) The required amount: n (C₇H₆O₃) = 11 x n (C₄H₆O₃) = 11 x 97.95 = 1 077.5 moles. Therefore, C₇H₆O₃ is the limiting reactant. It will be used fully.

The consumed amount of C₄H₆O₃ = n (C₄H₆O₃) / 11 = 97.95 / 11 = 8.9 moles

b) The remaining amount of C₄H₆O₃ = 97.95 - 8.9 = 89.05 moles

The remaining mass of C₄H₆O₃ = 89.05 x 97.95 = 8 722 g

c) n (C₉H₈O₄) = n (C₇H₆O₃) / 11 x 9 = 72.4 / 11 x 9 = 59.24 mol

m (C₉H₈O₄) = n x M = 59.24 x 180.16 = 10 672 g

d) m (C₉H₈O₄)_70% = 10 672 x 0.7 = 7 470 g