- If 600 mL of a Ba(OH) 2 solution are needed to neutralize 300 mL of a 4 M HC solution, what is the molarity of the Ba(OH) 2 solution?

Answer 1

Molarity (M) of the Ba(OH)₂ solution = moles Ba(OH)₂ / liter.

We know the liters (600 ml = 0.600 liters), so we need to find the moles of Ba(OH)₂.

Look at the balanced equation for reaction of Ba(OH)2 with HCl

Ba(OH)₂ + 2HCl ==> 2H₂O + BaCl₂ and from this we can determine the moles of Ba(OH)₂ as follows:

300 ml HCl x 1 L/1000 ml x 4 mol HCl/L x 1 mol Ba(OH)₂ / 2 mol HCl = 0.6 mol Ba(OH)₂

Molarity of Ba(OH)₂ = moles/L = 0.6 mol/0.6 L = 1 M (to 1 sig. fig. since 600 ml and 300 ml have 1 s.f.)