What would be the concentration of a solution made by adding 250 mL of water to 45.0 mL of 4.2 M KOH?
The concentration of the solution would be 0.64 mol/L.
One way to calculate the concentration of a diluted solution is to use the formula
Solve the formula for
Remember that the number of moles is constant
This makes sense. You are increasing the volume by a factor of about 7. So the concentration should decrease by a factor of about 7.