Question

You are asked to prepare 50 mL of a 2 g/L solution of CaCl2. you have a stock solution of 140 g/L. How many mL of the stock do you need to dilute to 50 mL to get this concentration?

If you mix 7 mL of a 340 g/L stock solution of KCl in a total volume of 1000mL, what is the KCl concentration in your solution? Answer in g/L.

Answer 1

Ans 1):

The equation required to calculate volume of stock solution can be written as follows:

C1V1=C2V2

Where,

C1 = concentration of initial stock solution = 140g/L

V1= volume of initial stock solution

C2= concentration of final solution = 2g/L

V2 = volume of final solution = 50mL

Thus, volume of stock solution required can be calculated as follows:

V1 = C2V2/C1

V1 = (2g/L x 50mL)/140g/L

V1 = 0.714mL

Thus, 0.714mL of stock solution is required to make desired CaCl2 solution.

Ans 2):

The equation required to calculate concentration of KCl solution can be written as follows:

C1V1=C2V2

Where,

C1 = concentration of initial solution = 340g/L

V1= volume of initial solution = 7mL

C2= concentration of final solution

V2 = volume of final solution = 1000mL

Thus, concentration of prepared KCl solution can be calculated as follows:

C2 = C1V1/V2

C2 = (340g/L x 7mL)/1000g/L

C2 = 2.38g/L

Thus, concentration of KCl solution is 2.38g/L