Question

A solution of 10 M NaOH was used to prepare 2 L of 0.5 M NaOH. How many mL of the original NaOH solution are needed?

Answer 1

The equation to solve problem is (M1) (V1) = (M2) (V2)
M1= 10M, V1= original NaOH solution, M2= 0.5 M, V2= 2L
First, the answer needs to be in ml., so convert 2L to ml = 2000ml
(10M) (V1) = (0.5M) (2000ml)
(10M)(V1) = 1000 M/ml
V1 = 1000M/ml / 10M, the Mmoles cancel out leaving just ml.
V1 = 100ml, which is the original NaOH solution needed.