# A. Identify the limiting reagent. B. State how many grams of the excess reagent remain. C. State how many grams of product are produced.?

## Aspirin (C9H8O4, molecular mass 180.2 g/mol) is synthesized by the reaction of salicylic acid (C7H6O3, molecular mass 138.1 g/mol) with acetic anhydride (C4H6O3, molecular mass 102.1 g/mol) according to the reaction 2 C7H6O3 (s) + C4H6O3(l) → 2C9H8O4(s)+ H2O(l) 2.0g of salicylic acid and 5.4 g of acetic anhydride are mixed and the reaction is allowed to go to completion. Do each of the following: A. Identify the limiting reagent. B. State how many grams of the excess reagent remain. C. State how many grams of product are produced.

Sep 5, 2017

This is a pretty complex stoichiometry question. I remember answering a similar question on my first general chemistry exam...

2C_7H_6O_3 (s) + C_4H_6O_3(l) → 2C_9H_8O_4(s)+ H_2O(l)

We want to build an ICF chart relating how many moles are produced or reacted in this reaction:

$2.0 g \cdot \frac{{C}_{7} {H}_{6} {O}_{3}}{138.1 g} \approx 1.45 \cdot {10}^{-} 2 m o l$
$5.4 g \cdot \frac{{C}_{4} {H}_{6} {O}_{3}}{102.1 g} \approx 5.29 \cdot {10}^{-} 2 m o l$

$1.45 \cdot {10}^{-} 2 m o l \cdot \frac{{C}_{4} {H}_{6} {O}_{3}}{2 {C}_{7} {H}_{6} {O}_{3}} = 7.25 \cdot {10}^{-} 3 m o l$

Below the initial reaction, I built the table with the data, from this table we can answer your questions.

(1) The limiting reagent is salicylic acid.
(2) Approximately $6.22 g$ of the excess reagent (acetic anhydride) remain.
$4.51 \cdot {10}^{-} 2 m o l \cdot \frac{138.1 g}{m o l} \approx 6.22 g$
(3) Approximately $2.61 g$ of aspirin are produced given this data.
$1.45 \cdot {10}^{-} 2 m o l \cdot \frac{180.2 g}{{C}_{9} {H}_{8} {O}_{4}} \approx 2.61 g$