Question

If I have 450mL of a 3.5 M HCl solution, what will the new molarity be if the volume is increased to 0.9L?

Explain your answer, please.

Answer 1

1.75M

Step-by-step explanation:

Given parameters:

Initial volume of acid, HCl = 450mL = 0.45L

Initial concentration = 3.5M

Final volume = 0.9L

Unknown:

Final concentration = ?

Solution:

This is a dilution problem in which a particular concentration is made from the stock of known concentration.

One important approach to solve this problem is to remember that the number of moles in the initial and final solution will always remain the same.

Since we know this;

Number of moles = molarity x volume;

let us find the number of moles of the initial solution;

Number of moles = 3.5 x 0.45 = 1.58moles

Now, to find the new molarity;

Molarity =
`(number of moles )/(volume)`

Input the parameters;

Molarity =
`(1.58)/(0.9)` = 1.75M