Question

Chloroacetic acid has a relatively large equilibrium constant, so at low acid concentrations it is necessary to use the quadratic equation in order to calculate the concentrations of the aqueous species. Ka for ClCH2COOH is 1.4 ´ 10-3. For the problems that follow, consider one liter of a solution that originally had 0.0200 mol of chloroacetic acid.


What is the equilibrium concentration of [ClCH2COOH]?



a. 0.010

b. 0.012

c. 0.015

d. 0.017

Answer 1

ClCH2COOH ==> ClCH2COO^- + H^+

Ka = (H^+)(ClCH2COO^-)/((ClCH2COOH)
(H^+)=x
(ClCH2COO^-)=x
(ClCH2COOH) = 0.02-x

Answer 2

a. 0.010

Answer 3

The answer is C).015

Find x through the quadratic equation x^2^ +(1.4E-3)x - (2.8E-5)=0