Question

How much concentrated solution do you measure out and how much water do you need to add to make 500ml 0.1M HCl from 2M HCl?

Answer 1

25mL of the 2M concentrated solution diluted to 500mL with 475mL water.

Explanation:

Using the concept of equivalents, the product of the molarity and the volume of one condition will equal those of the other.

`M_1*V_1 = M_2*V_2`

`2.0M * V_1 = 0.100M * 500mL`

`V_1 = (0.100M * 500mL)/2 = 25mL`
Therefore, you need to take 25mL of the 2M concentrated solution and dilute it into 475mL water.

In practice a volumetric flask would be used to ensure that the final total volume is 500mL.

ALSO - NEVER pour the water into the acid!!! ALWAYS pour acid (or bases) into water. Otherwise, the rapid exothermic solution process can cause spattering of the concentrated acid or base out of the container and onto persons or object nearby.