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### Practice Problem 1 Solution:

```If only 0.25 molar NaOH and water are available, how much NaOH
needs to be added to make 10 liters of 0.2 molar solution of NaOH?

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:

Molaritynew= Molarityoriginal*Volumeoriginal/Volumenew

.20 = .25*Volumeoriginal/10

Volumeoriginal=8 L

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