What volume of 0.5M CaCl2 solution is needed to prepare 250 ml of 0.5 ml of solution that has Cl- concentration 0.1 M?
A 12.5 ml
B. 25 ml
C.50 ml
D.200 ml
First the Molarity of the CaCl₂ from the molarity of the Cl⁻ ions is calculated.
Molarity of CaCl₂ in the concentration of 0.1M of Cl⁻ ionis is :-
0.1M / 2 = 0.05M of CaCl₂
since of M₁V₁ = M₂V₂
(Where M₁ is the molarity of the first solution,
V₁ is the volume of the first solution,
M₂ is the concentration of the second solution,
V₂ is the volume of the second solution)
The volume required is M₁V₁ = M₂V₂
0.5M × V₁ = 0.05M × 250/1000
V₁ = 0.05 × 0.25 / 0.5
= 0.025 L or 25 ml