Hey, have this question which i just cant wrap my head around, any help would be appreciated.

 

Formic Acid (HCOOH) - pKa = 3.8 is a weak acid that partially dissociates to form its conjugate base (HCOO-) and releases protons into aqueous solutions. Whats the pH of a solution in which (HCOOH) = .7M and (HCOO-) = .15M?

 

Then, if the pH of sol. of Formic acid has been titrated to a final pH of 2.8, Whats the ratio of conjugate base : Weak acid?

 

And suppose your given stock solutions of formic acid and sodium salt of the conjugate base : (HCOOH) = 3.OM and (HCOONa) = 1.5M,

How would you make a .1 M buffer(total formic acid + sodium formate concentration), 100mL total at pH 3.5, using above solutions?

I would use the Henderson Hasselback Equation for the first 2 questions in your problem.