Question

Nitric acid and propionic acid (CH3CH2CO2H) were combined to give 200. mL of an aqueous solution with a total solute concentration of 0.200 M (before dissociation of each acid). The pH of the solution (after equilibrium was reached) was 1.50. Ka = 1.3 x 10-5 for propionic acid. Kw = 1.0 x 10-14. What were the equilibrium concentrations of hydrogen ion, nitrate ion, propionate ion, and propionic acid in the solution?

Answer 1

Ans--- propionic acid dissociates as follows

CH3CH2COOH +H2O <======> H+ + CH3COO-

Initial concentration , 0.200 0 0

at equilibrium 0.200 -x x x

ka=[H+][CH3COO-]/[CH3COOH]

1.3*10^-5=x2/.200-x , since the value of Ka is very small , so x in the denominator is ignore.

x2= 1.3*10^-5(0.200)

x2=0.26*10^-5

x=0.0016

hence at equilibrium , [H+]=0.0016 [CH3CH2COO-]=0.0016 , [CH3CH2COOH]=0.200-X=0.200-0.001=0.199

HNO3 +H20 ====> H+ + NO3-

AT equilibrium , , [H+]=0.0016 , [NO3-]=0.0016 , [HNO3 ]=0.199

answered by: anonymous