Cara mencari ion OH- dalam larutan, jika 20 gram Na OH ( Ar Na=23, O=16, H=1). Dilarutkan dengan air sampai volume 5 L

20 gram NaOH (Ar Na = 23; O = 16: H = 1)
V = 5 L = 5000 mL

[OH^-] ... ?

*Mr NaOH
Mr = Ar Na + Ar O + Ar H
Mr = 23 + 16 + 1
Mr = 40

*Konsentrasi NaOH
M = gram/Mr × 1000/mL
M = 20/40 × 1000/5000
M = 0,5 × 0,2
M = 0,1

*[OH^-] = b × Mb
[OH^-] = 1 × 0,1
[OH^-] = 0,1
[OH^-] = 10^-1 M