Question

Dilute laboratory bench reagents are generally 6.0 M. What volume of dilute HCI must be used to prepare 500 mL of 0.25 M HCI?

Answer 1

Volume required ≈ 20.8 mL

Dilutions:

When a solution is diluted, the total number of moles of solute (n), does not change. Only the total solution volume changes. As n=cV (molarity formula, where n = moles, c = concentration, V = volume), then the value of cV is a constant when diluting solutions. This can be expressed by the ratio:

c₁V₁ = c₂V₂, where subscripts 1 and 2 represent the concentrated and dilute solutions.

To dilute a solution of 6.0 M HCl to 0.25 M with a total volume of 0.500 L, we can use the dilution formula, where initial and final concentrations = 6.0 M and 0.25 M respectively, and final volume = 0.500 L (500 mL).

Hence, 6.0×V₁ = 0.25×0.500 = 0.125

V₁ = 0.125/6.0 = 0.02083 L

Therefore, the volume we require is ≈ 20.8 mL