posted by stacy on .
Acetic acid (CH3COOH) reacts with isopentyl alcohol (C5H12O) to yield the ester isopentyl acetate which has the odour of bananas. If the yield from the reaction is 45%, how many grams of isopentyl acetate are formed when 3.77 g of acetic acid and 7.46 grams of isopentyl alcohol are reacted?
CH3COOH + C5H12O ¨ C7H14O2 + H2O
This is a limiting reagent problem. How do I know? Because BOTH reactants are given. Limiting reagent problems are solved, basically, by working two simple stoichiometry problems as follows:
1. Convert grams CH3COOH to moles. moles = grams/molar mass.
2. Convert grams C6H12O to moles with the same process.
3a. Using the coefficients in the balanced equation, convert moles moles CH3COOH to moles of the ester.
3b. Same for moles C6H12O.
(Note: Steps 1 and 3a are one simple stoichiometry problem; steps 2 and 3b are the other.)
(Note: Then you decide WHICH of the simple stoichiometry problems is correct.)
3c. The answer from 3a and 3b likely will be different which means one of them is wrong. The correct answer in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
4.Using the smaller value from step 3c, convert moles to grams. g = moles x molar mass. That is the theoretical yield.
5. %yield = (actual yield/theoretical yield)* 100 = ??
You know %yield and theoretical yield, solve for actual yield.