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The volume of the stock solution needed is 8 mL

Data obtained from the question

  • Molarity of stock solution (M₁) = 5 M
  • Volume of diluted solution (V₂) = 20 mL
  • Molarity of diluted solution (M₂) = 2 M
  • Volume of stock solution needed (V₁) =?

How to determine the volume needed

M₁V₁ = M₂V₂

5 × V₁ = 2 × 20

5 × V₁= 40

Divide both side by 5

V₁ = 40 / 5

V₁ = 8 mL

Learn more about dilution:

https://brainly.com/question/15022582

8 ml of a 5M solution is need to prepare a 20 ml of a 2M solution.

Molar concentration

To compare the molar concentration of two equal solutions we can use the following expression:

                                             [tex]C_{i} \times V_{i} = C_{f}\times V_{f}[/tex]

Thus, applying the values ​​given by the statement, we can assemble the following expression:

                                           [tex]5 \times V = 2 \times 20[/tex]

                                                [tex]V = 8 ml[/tex]

So, 8 ml of a 5M solution is need to prepare a 20 ml of a 2M solution.

Learn more about mole calculation in: brainly.com/question/2845237

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