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Topic: Making up solutions with non-water solvent  (Read 2019 times)

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Offline zeoblade

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Making up solutions with non-water solvent
« on: August 10, 2010, 12:02:03 AM »
I just want to solve a stupid debate about molarity.

Solute = benzyl alcohol
Solute density at 20oC= 1.0453g/mL
Solute molecular mass = 108.13g/mol
Needed concentration = 0.25M
Needed volume = 10mL
Solvent = CCl4

mol solute needed = 0.25mol/L x 0.01L = 0.0025mol
A) Mass solvent needed = fill up to 10mL

OR

B) Mass solvent needed = 10mL x 1.0453g/mL = 10.4530g
This means that 10mL mark will be exceeded.

What is the correct method? If I could get the person to post you a chocolate bar for winning this bet, I would.

Offline Borek

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Re: Making up solutions with non-water solvent
« Reply #1 on: August 10, 2010, 04:13:02 AM »
This is molarity vs molality.

Molarity is per volume, so you should fill up to 10 mL.

Molality is per solvent mass, so if preparing molal solution you should use 10.45 g of the solvent.
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