Answer:
Measure 20mL of the stock
Explanation:
All we need to do is to find the volume of the stock solution needed. This is illustrated below:
C1 = 2M
V1 =?
C2 = 0.400 M
V2 = 100mL
C1V1 = C2V2
2 x V1 = 0.4 x 100
Divide both side by 2
V1 = ( 0.4 x 100) /2
V1 = 20mL
Therefore, to prepare the solution, we will measure 20mL of the stock solution and make it up to the 100mL mark.
The working solution has been prepared by dissolving 20 mL of stock solution and make up the volume to 100 mL.
The preparation of working solution from the stock has been done by diluting the stock solution to the required concentration.
The volume of stock required for the dilution has been given as:
[tex]M_1V_1=M_2V_2[/tex]
Where, the molarity of stock solution, [tex]M_1=2\;\rm M[/tex]
The molarity of working solution, [tex]M_2=0.4\;\rm M[/tex]
The volume of working solution, [tex]V_2=100\;\rm mL[/tex]
The volume of stock solution, [tex]V_1[/tex] to be dissolved in working solution to make the dilution has been calculated by substituting the values in above equation as:
[tex]2\;\times\;V_1=0.40\;\times\;100\;\text{mL}\\V_1=\dfrac{40}{2}\;\text {mL}\\V_1=20\;,\rm L[/tex]
The volume of stock solution required for the preparation of working solution has been 20 mL.
For more information about stock solution, refer to the link:
https://brainly.com/question/10550424
