Molarity problem, need help?

Question

how much water would I need to add to 20.0mL of 2.0M NaCl to make a 0.10 M solution?

Answer 1

CV = CV
where C = concentration (Molar = moles/Liter, a concentration) and V = total volume of liquid
(2.0 moles/L)*(.02 L) = (.1 moles/L)*(x L)

x = (2)(.02)/(.1)
x=.4 L (but you already have .02L) so .38L

Answer 2

V2 = M1V1/M2
= (20.0mL * 2.0M NaCl) / 0.10 M
= 400 mL

V2 means volume of final solution which means
v2 = v1 + water
water = v2- v1 = 400 - 20 = 380 mL H2O

Answer 3

Since salt is conserved:
20ml x 2M = V ml x 0.1 M
solve for V.

Answer 4

let x = volume of water

solution:

(20ml)(2.0M) = x (0.10M)
x = (20 ml) (2.0 M) / (0.1M)
x = 400 mL