find concentration of a diluted solution that is formed by placing 5.3 mL of this “stock” (or concentrated) HCl solution in another volumetric flask and adding water to make a total of 25.0 mL?

Question

A “stock” solution was made by placing 50 mL of 3.0 M HCl in a volumetric flask and adding water to double the volume. 

Answer 1

For simple dilutions such as this, one can use V1M1 = V2M2 where...

V1 = initial volume

M1 = initial concentration

V2 = final volume

M2 = final concentration

For this problem, we will use this formula twice. First to find the initial concentration of the HCl "stock".

(50 ml)(3.0 M) = (100 ml)(x M); the 100 ml is because it tells us the volume was doubled

x = 1.5 M HCl "stock"

Next, we dilute this stock and use the formula again:

(5.3 ml)(1.5 M) = (25.0 ml)(x M)

x = 0.318 M = 0.32 M (2 sig. figs.)