Ka for HF is 6.8x10-4. Calculate the pH of a 0.35 M solution of HF?

 

i dunno how to do it

Hope this is correct: (Sorry for the scruffy handwriting)

 

The important part is to know the formula for Ka and how to use it.

neo, I can not see the attached picture (?)

 

Ka for HF is 6.8x10-4. Calculate the pH of a 0.35 M solution of HF?

 

i dunno how to do it

As always, start from the definitions.

 

What is the definition for (or formula describing) Ka of an acid ? Now apply it to the case of HF. To find relations between the quantities in your equation, write down the equilibrium reaction for ionization of HF in aqueous solution.

 

And what about pH ? How is it defined ? What do you need to know to find its value ? Is this quantity found in the above equation ?

The picture works for me, you can see it here:

http://img154.echo.cx/img154/1750/10000118vw.jpg

but it should work... I don't know if it is correct though (because I don't know how to answer the question, not because I'm not sure if he's right!)

I see it now. Thanks for the link anyway.

 

Neo's solution is correct.