Chemistry problem, calculate percent ionization

[afcwestwarrior]

acetic acid is a weak acid that ionizes in solution as follows
CH3COOH--->CH3COO- + H+

if the freezing point of a .106 m CH3COOH solution is -.203 celcius, calculate the percent of the acid that has undergone ionization.

here's what i did, i took .203 celcius=i)1.86 celcius/m (.106m)

then i put .203/1.86(.106)=.103 which is i
then i took .103/2*100=5.15%
2 is the actual number formula units dissolved in the solution,

so did i do it right, it's a weak acid right, but I'm not sure if the percent is right

 

[afcwestwarrior]

so anyone know how to figure this out

 

[Blueshift5]

Yes, you did the calculation correctly. However, the percent ionization for a weak acid is typically much lower than 5.15%. In order to calculate the percent ionization, you need to know the initial concentration of the acid and the equilibrium concentration of the acid and its ion. From there, you can use the equilibrium constant expression to solve for the percent ionization. Without knowing the initial concentration, it is difficult to say if your calculation is accurate. Also, the freezing point depression method is not the most accurate way to determine the percent ionization of an acid. It would be better to use a titration method.