Answer:
75 mL
Step-by-step explanation:
The key point to remember is that the amount of solute is the same in each solution.
amount of solute = concentration
c₁V₁ = c₂V₂
V₂= V₁ × c₁/c₂
Data:
V₁ = 100 mL
c₁ = 20 %; c₂ = 80 %
Calculations:
(a) V₂
V₂ = 100 × (20/80) = 25 mL
(b) Added diluent
You have 25 mL of stock solution, and you want 100 mL of dilute solution, so you add 75 mL of diluent.
