What will the final concentration be if I dilute a solution of 16g/L by adding 1 ml to 9 ml of water, and then 1 ml to 99 ml of water?

Question

Please can someone explain how to solve these types of questions

Answer 1

Hi Emily!

When you're going between two dilutions, you can use the formula M1V1 = M2V2 where M1 is the concentration of the first solution, V1 is the volume of the first solution, M2 is the concentration of the second solution, and V2 is the volume of the second solution.

Also keep in mind for these questions that the volume of the second solution is both the amount of the first solution plus the water you're diluting with! So if you've got 5 gallons of solution and you're diluting with 6 gallons, your second (and final) volume is 11 gallons.

For your first question, you're diluting a solution of 1 mL to 10 mL (total, 1mL + 9mL).

M1 = 16 g/L

V1 = 1 mL

M2 = ???

V2 = 10 mL

Make M2 = x, and solve for x.

(16)(1) = (x)(10)

x = 16/10

x = 1.6

So, your new concentration is 1.6 g/L.

You can repeat this process for the second question:

M1 = 16 g/L

V1 = 1 mL

M2 = ???

V2 = 100 mL (1 mL + 99 mL)

(16)(1) = (x)(100)

16/100 = x

x = 0.16

So, your new concentration is 0.16 g/L.

Hope this helps!