Answer to Question #125422 in Physical Chemistry for Shanaya Nand

Question

Ethanoic acid and ethanol react reversibly to form ethyl ethanoate and water. (It doesn't matter if you have never come across this before.) In a closed system, a dynamic equilibrium is set up.ethanoic acid ethanolethyl ethanoatea) Suppose you now added some more ethanol. What effect would that have on the percentage of ethanoic acid converted into ethyl ethanoate. Explain your answer using Le Chatelier's Principle.b) This reaction is fairly slow, and is usually done in the presence of a small amount of concentrated sulphuric acid as a catalyst to speed it up.(i) What effect would that have on the percentage of ethanoic acid converted into ethyl ethanoate? Explain your answer.(ii) (You will need to think about this one! It isn't covered on the page you have just read, but it is still about Le Chatelier's Principle.) If you wanted to make as much ethyl ethanoate as possible, why would it be a bad idea to use dilute sulphuric acid as the catalyst

Answer 1

The reaction equation of ethanoic acid and ethanol is:

According to Le Chatelier's Principle, when you add ethanol, the equilibrium will shift in a way to compensate the change in the system. Therefore, the equilibrium will shift to the right, boosting the formation of ethyl ethanoate.

When the catalyst is added, both forward and backward reactions are speeded up. Therefore, the addition of the sulphuric acid doesn't have any effect on the equilibrium and therefore on the percentage of ethanoic acid converted to ethyl ethanoate. However, when the solution of the sulphuric acid is added, the water, inevitably present in aqueous solution as a solvent shifts the equilibrium to the left, boosting the hydrolysis reaction. Thus, addition of dilute sulfuric acid as a catalyst will shift the equilibrium to the left and will favor the formation of ethanoic acid and ethanol.