In dilution problems involving known concentrations and volumes of the solution, a widely used equation is:
C1V1 = C2V2
Where:
C1 = Concentration of Solution 1
V1 = Volume of Solution 1
C2 = Concentration of Solution 2
V2 = Volume of Solution 2
Substituting the given values gives: (2.35 M)*(250mL) = (15.0 M)*V2
V2 = 39.17 mL
So, you must initially have 39.17 mL of 15 M solution and dilute it to 250 mL to achieve a 2.35 M solution
