I've got a buffer question....?

Question

What masses of acetic acid and of sodium acetate will be needed to prepare 5.00L of an acetate buffer with a pH of 3.75 and a total acetic acid-acetate concentration of 0.150 M?

It would be great if you could go through this step by step. Thanks!

Answer 1

pH = pK + log (salt)/(acid)
Ka = 1.8 10^-5
pKa = -log 1.8 10^-5= 4.74
3.75 = 4.74 + log (salt)/(acid)
- 0.995 = log (salt)/(acid)
10^-0.995 = (salt)/acid)
0.101 =( salt)/acid)

we know that total concentration is 0.150 M

we make a system
0.101 =(salt)/(acid)
(salt)+(acid )= 0.150

(salt )=0.150-(acid)
0.101 = 0.150-(acid)/(acid)

0.101 (acid) = 0.150-(acid)
1.101(acid )=0.150
(acid )= 0.136 M

(salt )= 0.150-0.136=0.014M

0.136 M means 0.136 mole in 1 L>> in 5 L 0.68 mole
MM (CH3COOH)=60 g/mol
0.68mole(60 g/mole)=40.8g

0.014(5)= 0.07 mole
MM(CH3COONa)=82
82 (0.07)=5.74 g

(...) means concentration

Answer 2

no idea