Answer to Question #225158 in Chemistry for Junior

Question

Calculate the mass of potassium hydroxide, KOH, required to prepare a 200 mL

solution that was diluted to give a concentration of 0.030 mol/L. The solution has

a dilution factor of 5.

Answer 1

V₁ = 200 mL

C₂ = 0.030 mol/L

Dilution factor = 5

Solution:

C₁V₁ = C₂V₂

Dilution factor = C₁/C₂ = V₂/V₁

Dilution factor = Final solution volume (V₂) / Volume from stock solution (V₁)

Therefore,

Final solution volume (V₂) = Dilution factor × Volume from stock solution (V₁)

V₂ = 5 × (200 mL) = 1000 mL = 1 L

Calculate the moles of KOH:

n(KOH) = C₂ × V₂ = (0.030 mol/L) × (1 L) = 0.030 mol KOH

The molar mass of KOH is 56.1 g/mol

Therefore,

(0.030 mol KOH) × (56.1 g KOH / 1 mol KOH) = 1.683 g KOH = 1.68 g KOH

Answer: 1.68 g of KOH is required to prepare a 200 mL solution.