Question

If you dilute 18.8 mL of a 3.5 M solution to make 296.6 mL of solution, what is the molarity of the dilute solution?

Answer 1

Answer:

0.22M

Explanation:

We will be using the law of dilutions. We are simply increasing the amount of solvent to create a larger volume of solution.

So: moles before dilution = moles after dilution & $moles_{concentrated} = moles_{dilute}$. And M = moles/liter of solution, so if we express this as moles = M x $L_{soln}$.

That is how we derive the formula we will be using: $M_{concentrated} * Vol_{conc} = M_{dilute} * Vol_{dilute}$

or

$M_{1} * Vol_{1} = M_{2} * Vol_{2}$

Applying this formula to our problem, we can substitute the variables with the given values to find the molarity of the dilute solution.

M1 = 3.5M

V1 = 18.8mL

M2 = ?

V2 = 296.6mL

Equation: (3.5M)(18.8mL) = (296.6mL)(M2)

==> 65.8M*mL = 296.6mL * M2

==> M2 = (65.8 M*mL)/296.6mL

==> M2 = 0.22M