We need to add 2 liters of water !
Explanation:
Here we have , I have 4.0 L of a 3.0 M NaCl solution and I want to dilute it to 2.0 M. We need to find How much water do I need to add. Let's find out:
4.0 L of a 3.0 M NaCl solution , i.e.
⇒ Molarity = ( Number of moles ) / ( Volume of solution in L )
⇒ [tex]Molarity = \dfrac{n}{V}[/tex]
⇒ [tex]3 = \frac{n}{4}[/tex]
⇒ [tex]n=12[/tex]
Now , Molarity is changed to 2M i.e.
⇒ [tex]2 = \frac{12}{V}[/tex]
⇒ [tex]V=6[/tex]
So , change in volume is : [tex]6L-4L[/tex] = [tex]2L[/tex]
Therefore , We need to add 2 liters of water !
