How many ml of 21% stock solutions do you need , if you need to prepare 360ml of 10% using 21% and 3% solutions?

Answer 1

Let's assume the amount of 21% stock solution needed is x ml.

We know that the total volume of the 10% solution to be prepared is 360 ml.

So, the amount of 3% solution needed would be (360 - x) ml.

We can create an equation based on the concentration of the solutions:

21%(x) + 3%(360 - x) = 10%(360)

Simplifying the equation:

0.21x + 0.03(360 - x) = 0.10(360)

0.21x + 10.8 - 0.03x = 36

0.18x = 36 - 10.8

0.18x = 25.2

x = 25.2 / 0.18

x ≈ 140

Therefore, you will need approximately 140 ml of the 21% stock solution.