Question

You wish to make a 0.445 M hydrochloric acid solution from a stock solution of 12.0 M hydrochloric acid. How much concentrated acid must you add to obtain a total volume of 150 mL of the dilute solution?

Answer 1

To obtain a total volume of 150 mL of the dilute solution we have to take 5.5 ml of stock solution

The solution is as follows,

step 1]we need to find how much acid should be in the final solution and then find the volume of initial solution containing that amount of acid:

0.445 M solution means that 1 L of solution contains 0.445 moles of acid. Then 150mL (0.150 L) of such solution contains (0.150 L/1L) * 0.445 mol = 0.06675 moles.

step 2] we also need to find the amount of stock solution containing 0.06675 moles of acid,

1 L of 12M solution contains 12 moles of acid. Then 0.06675 moles is in (0.06675 moles/12 moles) * 1L = 0.0055 L = 5.5 mL.