Question

If you have a 500 mL of a 0.4M Nacl solution. How much water is needed to make is 0.1M solution?

Answer 1

moles = molarity(M) x volume(L) = 0.4 x 500 / 1000 = 0.2 moles

0.2 moles in 2L = 0.1M
So you need 1.5L water