Answer to Question #108844 in General Chemistry for LPX

Question

4.!!An aqueous solution containing ethanol and acetic acid, both at initial concentration of 0.810molL-1 are heated to 100oC. Reaction occurs between the alcohol and the carboxylic acid to form the ester, ethyl acetate. C2H5OH (aq) + CH3COOH (aq) CH3COOC2H5 (aq) + H2O (l) At equilibrium, the acetic acid concentration is 0.748 molL-1. Calculate K for the reaction at 100oC.

Answer 1

K = [CH3COOC2H5]*[H2O]/([C2H5OH]*[CH3COOH]) ;

Let's suppose that the volume of the solution is 1 liter, then the initial amount of reactants is:

n(C2H5OH) = n(CH3COOH) = 0.81 mol;

If at equilibrium, the acetic acid concentration is 0.748 molL-1 , then the amount of the acid and alcohol respectively that reacted is:

n(CH3COOH)=n(C2H5OH)= 0.81-0.748=0.062 mol;

From the reaction we can understand that n(CH3COOH)=n(CH3COOC2H5)=n(H2O)=0.062 mol;

So, at  equilibrium: [CH3COOC2H5]=[H2O]=0.062 mol/L;

[C2H5OH]=[CH3COOH]=0.748 mol/L;

K=(0.062*0.062)/(0.748*0.748) = 0.00687;

Answer: K for the reaction at 100oC is 0.00687