[blackflag10]

I have a test tomorrow morning; my professor is out of town, and I cannot figure out this problem in my prep packet.  Please help. 

A solution that contains 0.100 g of a weak acid, HA, (MW=100 g/mol) and 500 g of H20 has a freezing point of -0.0056 Celsius. If the density of the solution is 1.01 g/mL and Kf for H20 is 1.86, calculate the Ka for the weak acid HA


I know how to do freezing point depression formula to find the molality, but I am not sure where to go after I do that.  Please *delete me*!


Thank you

[Borek]

Use the information given to calculate number of ions/molecules in the solution - then use this information to calculate how much of the acid has to be dissociated. This is about understanding what Van 't Hoff factor is.

[blackflag10]

Use the information given to calculate number of ions/molecules in the solution - then use this information to calculate how much of the acid has to be dissociated. This is about understanding what Van 't Hoff factor is.

Can you quickly walk me through that please?  I am pretty sure we did not talk about the Van't Hoff factor though.

[Borek]

http://en.wikipedia.org/wiki/Van_'t_Hoff_factor