Question

A student reacts 37g of salicylic acid with 60 mL of acetic anhydride producing 26.7g of acetyl salicylic acid. What is the percent yield of the reaction

Answer 1

The reaction between salicyic acid (C₇H₆O₃) and acetic anhydride(C₄H₆O₃) produces acetyl salicylic acid (C₉H₈O₄ ) is       C₇H₆O₃ + C₄H₆O₃ → C₉H₈O₄ + CH₃COOH

Molar mass of salicyic acid (C₇H₆O₃) is = ( 7x12) + (6x1) + ( 3x16)

                                                               = 138 g/mol

Molar mass of acetyl salicylic acid (C₉H₈O₄ ) is = ( 9x12) + (8x1) + ( 4x16)

                                                              = 180 g/mol

According to the balanced equation,

1 mole of salicylic acid produces 1 mole of acetyl salicylic acid                                                       

                                          OR

138 g of salicylic acid produces 180 g of acetyl salicylic acid       

37 g of salicylic acid produces M g of acetyl salicylic acid

M = ( 37 x 180 ) / 138

    = 48.3 g of acetyl salicylic acid     -------- This is the theoretical yield

Given actual yield is 26.7 g

So percent yield = ( actual yield / theoretical yield ) x 100

                          = ( 26.7 / 48.3) x 100

                          = 55.3 %

Therefore the percent yield of the reaction is 55.3 %