md = ? K₂O
Vsi = 120cm³ sol. KOH
Ci = 15%
ρ = 1,12g/cm³
Cfinal = 25%
ρ = msi/Vs ⇒ msi = ρ×Vs = 1,12×120 = 134,4g sol. KOH
Ci = mdi/msi×100 ⇒ mdi = Ci×msi/100 = 15×134,4/100 = 20,16g KOH
Cfinal = (mdi+md adaugat)/(msi+md adaugat) ×100 ⇔ 25 = (20,16+md ad)/(134,4+md ad)×100 ⇔ 3360+25md ad = 2016+100md ad ⇔ 75md ad = 1344 ⇒ md adauat = 17,92g K₂O