Question

What volume of a 0.50 M KOH solution is needed to neutralize completely each of the following?

i) 10.0 mL of a 0.30 M HCl solution

ii) 15.0 mL of a 0.25 M H3PO4 solution

Answer 1

part 1

millimoles of HCl = Molarity x volume in mL = 0.3M x 10 mL = 3 mmiol

let see the balanced equation

HCl + KOH ---> KCl + H2O

1 mol of HCl required 1 mol of KOH accordingly

3 mmol of HCl required 3 mmol of KOH

mmol of KOH = 3 mmol

volume of KOH = mmol / M olarity = 3 mmol / 0.5M = 6 mL

part B

mmol of H3PO4 = 0.25 M x 15 mL = 3.75 mmol

see the balanced equation

H3PO4 + 3KOH ---> K3PO4 + 3H2O

1 mmol of H3O4 required 3 mmol of KOH accordingly

3.75 mmol required 3 x 3.75 = 11.25 mmol of KOH

volume of KOH = 11.25 / 0.5 = 22.5 mL