Answer:
pH = 4,76
a) pH = 4,94
b) pH = 5,51
Explanation:
To calculate the pH of a buffer you must use Henderson-Hasselbalch formula thus:
pH = pka + log [tex]\frac{[A^-]}{[HA]}[/tex]
Where [A⁻] is acetate ion concentration and [HA] is acetic acid concentration
The concentration of acetic acid is:
0,5 L× 0,38 M ÷(0,5L+0,5L) =0,19 M
The concentration of acetate ion is:
0,5 L× 0,25 M ÷(0,5L+0,5L) = 0,125 M
The pH is:
pH = 4,76 + log [tex]\frac{[0,125]}{[0,19]}[/tex]
4,76
a) The concentration of acetic acid is:
0,4 L× 0,24 M ÷(0,4L+0,3L) =0,137 M
The concentration of acetate ion is:
0,3 L× 0,48 M ÷(0,4L+0,3L) = 0,206 M
The pH is:
pH = 4,76 + log [tex]\frac{[0,206]}{[0,137]}[/tex]
4,94
b) The reaction of NaOH with acetic acid produces acetate ions, thus, moles of NaOH will increase concentration of acetate ion and descrease acetic acid concentration, thus:
NaOH moles: 0,010L× 6M = 0,060 moles
The concentration of acetic acid is:
(0,4 L× 0,24 M) - 0,060 moles ÷(0,4L+0,3L) =0,0514 M
The concentration of acetate ion is:
(0,3 L× 0,48 M) + 0,060 moles ÷(0,4L+0,3L) = 0,291 M
The pH is:
pH = 4,76 + log [tex]\frac{[0,291]}{[0,0514]}[/tex]
5,51
I hope it helps!
