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April 19, 2014

Homework Help: science(chem)

Posted by ~christina~ on Wednesday, October 1, 2008 at 10:40pm.

I'm making different concentrations of
ethanol and I just wanted to check my calculations and method.

Making ethanol concentrations of:

0.40%
0.30%
0.20%
0.10%
0.05%

To make the 0.40% ethanol from stock solution using 100ml volumetric flask:

(xg ethanol)/(100ml) x 100= 0.40%
xg= 0.4g ethanol

Then 0.4g ethanol solution is added to a 100ml volumetric flask with water in it already. After the addition of 0.4g ethanol into the flask whilst weighing it on a balance.

Then I take that 0.40% solution of ethanol and dilute it with
M1V1=M2V2

To get 10ml of 0.30% ethanol solution:
Find out how much of stock is needed to dilute
(0.40%)(V1)=(0.30%)(10ml)
V1= 7.5ml ethanol

add that 7.5ml ethanol into a 10ml volumetric flask and add water to the line to get 0.3% ethanol solution

To get 10ml of 0.20% ethanol solution:
Find out how much of stock is needed to dilute
(0.40%)(V1)=(0.20%)(10ml)
V1=5 ml ethanol

add that 5 ml ethanol into a 10ml volumetric flask and add water to the line to get 0.2% ethanol solution

same process for the below concentrations..just checking my calculations:

0.1% ethanol solution:
(0.40%)(V1)=(0.10%)(10ml)
V1=2.5 ml ethanol

0.05% ethanol solution:
(0.40%)(V1)=(0.05%)(10ml)
V1=1.25 ml ethanol

I'm not sure if I can use percentage for the dilution equation, or if I can even use grams for the creation of the original solution

Thanks very much

Thanks

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