Question

help me..

The pKa of acetic acid, HC2H3O2, is 4.76. A buffer solution was made using an unspecified amount of acetic acid and 0.30 moles of NaC2H3O2 in enough water to make 2.00 liters of solution. Its pH was measured as 4.40. How many moles of HC2H3O2 were used?

Answer 1

I would do this.
pH = pKa + log (base)/(acid)
4.40 = 4.76 + log (base)/(acid)
base = 0.3/2 = ?
acid = x/2
Solve for x = mols acetic acid.