Concentration Solution

One way to do the problem:
You're going to take a certain number of moles contained in a volume and put these moles in a total volume such that the final concentration is 0.2 molar. First we can determine how many moles are needed to make 10 liters of solution that are 0.2 molar:

10 liters * 0.2 moles/liter = 2 moles

Now that we know we need 2 moles of NaOH, we can see how many liters of 0.25 molar solution are need to have 2 moles of NaOH:

2 moles * 1 liter/0.25 moles = 8 liters

Another way to solve this problem is to use the equation:

Molarity_new= Molarity_original*Volume_original/Volume_new

.20 = .25*Volume_original/10

Volume_original=8 L

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Developed by

Shodor
in cooperation with the Department of Chemistry,
The University of North Carolina at Chapel Hill