Question

Hitunglah pH larutan CH3COOH 0,5 M, jika diketahui Ka1 = 1,8 x 10^-5 dan Ka2 = 1,2 x 10^-13

Answer 1

Reaksi onisasi CH3COOH tahap 1
CH3COOH(aq)-->H+(aq) + CH3COO-(aq)
0,5 M
-xM +xM +xM
0,5M-x xM xM
~0,5 M
ka1 = [H+] [ CH3COO-]/ [CH3COOH]
1,8×10^-5 = x kuadrat/ 0,5
xkuadat = 9×10^-6
x = 3×10^-3
[H+] tahap 1 = x = 3×10^-3
[H+] kesetimbangan [H+]1 +[H+]2 +[H+] air
karna ka2 < ka1 maka [H+]1 >[H+]2 >[H+] air sehingga [H+] 2 & [H+] air dapat diabaikan
jadi [H+] kesetimbangan = [H+]1
= 3×10^-3M
pH = -log [H+]
= -log 3×10^-3M
= 3-log 3