1. What is the molarity of an HCl solution if 43.6 mL of a 0.125 M KOH solution are needed to titrate a 25.0 mL sample of the acid according to the equation below?
KOH(aq) + HCl(aq) → H2O(l) + KCl(aq)
The balanced chemical equation shows a 1:1 mole ratio between KOH and HCl. This means that the moles of KOH used in the titration will be equal to the moles of HCl in the sample.
First, calculate the moles of KOH used in the titration:
moles KOH = volume (L) x molarity
moles KOH = 0.0436 L x 0.125 mol/L
moles KOH = 0.00545 mol
Since the moles of HCl are equal to the moles of KOH:
moles HCl = 0.00545 mol
Now calculate the molarity of the HCl solution:
molarity = moles / volume (L)
molarity = 0.00545 mol / 0.025 L
molarity = 0.218 M
The molarity of the HCl solution is 0.218 M.