Berapa gram kristal NH4CL yg diperlukan untuk membuat 500 ml larutan dengan pH 5. (Ar H: 1 ; Ar N:14 ; Ar Cl:35.5. Kb NH3 10^-5)

pH = 5 -> [H+] = 10^-5
Kb = 10^-5
Mr = 53,5
maka, [H+] = akar kw/kb x M
10^-5 = akar 10^-9 x M
10^-10 = 10^-9 x M
10^-1 = M

M = n/v
10^-1 = n/0,5
0,1 = n/0,5
n = 0,2

n = m/Mr
m = n/Mr = 0,2 : 53,5 = 0,0037
i