8. 1:5 Dilution
A dilution factor of 1:5 means that the concentration of the new solution is ⅕ that of the original solution.
∴ c = ⅕ × 1 mol·L⁻¹ = 0.2 mol·L⁻¹
9. 1:10 Dilution
A dilution factor of 1:10 means that the concentration of the new solution is ⅒ that of the original solution.
∴ c = ⅒ × 5 mol·L⁻¹ = 0.5 mol·L⁻¹
10. Preparation of 0.25 mol·L⁻¹ solution
You are making a 1:4 dilution. This means that the volume of the new solution is four times that of the stock solution.
Thus, if you wanted to make 1 L of 0.25 mol·L⁻¹ solution, you would take
250 mL of the stock solution and add enough water to bring the volume up to 1 L.
