A solution NaOH(aq) contains 8.5 g NaOH(s) per 100.0 mL of solution. Calculate the pH and the pOH of the solution at 25 °C.

Question

ph=

pOH=

Answer 1

Molar mass NaOH = 40 g /mol

Moles NaOH present = 8.5 g NaOH x 1 mol / 40 g = 0.2125 moles

Molarity (moles/Liter) of NaOH = 0.2125 mol / 100.0 ml x 1000 ml / L = 2.125 moles NaOH / L

Molarity of OH- = 2.125 M since each mole NaOH produces 1 mol OH-

pOH = -log [OH-]

pOH = -log 2.125

pOH = -0.33

pH+pOH = 14

pH = 14 - pOH

pH = 14 - (-0.33)

pH = 14.33