How much do you need of 2 M NaCl to prepare 4 ml of 50 mM Na

How much do you need of 2 M NaCl to prepare 4 ml of 50 mM NaCl?

a. Add 10uL of 2M to 3.9mL of diH2O

b. Add 100uL of 2M to 390mL of diH2O

c. Add 1uL of 2M to 3.9mL of diH2O

d. Add 100uL of 2M to 3.9mL of diH2O

Solution

We will use the law of equivalence to solve this problem, i.e. N₁V₁ = N₂V₂, where N = normality and V = volume.

Thus, 2×V₁ = (50/1000)×4,

or V₁ = [(50/1000)×4]/2 = 0.1 mL, i.e. 100 L 2M NaCl would be required.

Volume of diH₂O = 4-0.1 = 3.9 mL

Therefore, option d is the most appropriate choice.