Question

What is the concentration of a solution formed by adding 65.0 mL of water to 25.0 mL of A 3.2 M NaCl solution?

Answer 1

Using the formula for dilution. 
C1V1 = C2V2
C1 = 3.2 M V1 = 25.0 mL V2 = 90.0mL (65 mL +25 mL)
C2 = C1V1/V2
= (3.2 M*25.0 mL)/90.0mL
= 0.89M
Thus, the new concentration will be 0.89 M