7 10pts You need 15mM Tris in a volume of 14mL You have 200m

7. (10pts) You need 15mM Tris in a volume of 14mL. You have 200mM Tris in a stock bottle on your bench.

• What volume of 200mM Tris do you need to make the 14mL of 15mM Tris?

• What volume of water do you need to make the 14mL of 15mM Tris?

8. (20pts) 13mL of 240mM Tris (MW= 121.14g/mol) is added to a tube containing 37mL of dH2O. What is the final molarity of this Tris solution? Show all of your work for full credit.

Solution

1. Solution No.7:

Stock Solution- 200mM, {(Initial Concentration(M₁)}

Working Solution- 15mM {(Final Concentration(M₂)}, 14 mL {Volume(V₂)}

According to formula:

Initial Concentration(M₁) X Volume(V₁) = Final Concentration(M₂) X Volume(V₂)

=> 200mM x V = 15mM x 14

=> V = (15 X 14)/ 200

=> V = 1.05 mL

Thus, 1.05 mL from a stock of 200 mM can be taken and 12.95 of distilled water can be added to make up the volume to 14mL of 15 mM working solution. Thus:

Volume of Stock of 200 mM required is = 1.05 mL

Volume of water required is = 12.95 mL

2. Solution No. 8:

Initial Concentration(M₁)= 240mM

Volume(V₁) = 13mL

Final Concentration(M₂)= Let it be \'M\'

Volume(V₂)= 37mL( distilled water) + 13mL (Tris solution) = 50 mL

According to formula:

Initial Concentration(M₁) X Volume(V₁) = Final Concentration(M₂) X Volume(V₂)

=> 240mM x 13mL = M x 50 mL(37+13= 50)

=> M = (240 X 13)/ 50

=> M = 62.4 mM = 62 mM

Thus, the resulting molarity of the solution will be 62mM.