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Need help calculating Molar Concentration

Need help calculating Molar Concentration - Chemistry Forum

Need help calculating Molar Concentration - Chemistry Forum. Discuss chemical reactions, chemistry.


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  #1  
Old 07-12-2003, 09:23 PM
Photon Beam
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Default Need help calculating Molar Concentration



If I have a dye with a molecular weight of 606 and I want to make a
solution with a molar concentration of 1.5 x 10-4, how many milligrams
of dye per liter of solvent will I need? What is the formula? Thank
you!
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  #2  
Old 07-12-2003, 09:44 PM
Repeating Decimal
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Default Need help calculating Molar Concentration

in article [Only registered users see links. ], Photon Beam at
[Only registered users see links. ] wrote on 7/12/03 2:23 PM:


Given the molecular weight, this is about as easy problem as you can get.

1. Look up molar or molarity.

2 Do the calculation. (Hint: multiply)

Knowledge is power!

Bill

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  #3  
Old 07-12-2003, 10:03 PM
Stephan Bird
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Default Need help calculating Molar Concentration

In article <[Only registered users see links. ]>,
[Only registered users see links. ] says...

Conc = Moles / Volume

where Moles = Mass / Molar Mass

Stephan
--
Stephan Bird MChem(Hons) AMRSC
[Only registered users see links. ]EMOVE
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  #4  
Old 07-12-2003, 10:41 PM
Art
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Default Need help calculating Molar Concentration

On Sat, 12 Jul 2003 23:03:20 +0100, Stephan Bird
<stephan.j.bird@mad.scientist.comREMOVE> wrote:


Sorry, I still don't get it. This page is helpful, but what are the
units of mass and volume in the formulas?
[Only registered users see links. ]
Is the molecular weight not a factor? I know this is high school
chemistry but it seems difficult to me. That's why I came here for
the answer. Thanks!
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  #5  
Old 07-13-2003, 02:20 AM
Tim
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Default Need help calculating Molar Concentration

Art wrote:


Some people are arrogantly pushing their degrees in your face. I am
sorry for their attitude toward you and your question. I hope the
following helps.

One mole of the dye would weigh 606 grams.
So, 1.5 moles would weigh 909 grams.

To make a 1 liter solution with a 1.5 molar concentration, you would
dissolve 1.5 moles (909 grams) in one liter of solvent. BUT, you want a
molar concentration that is 1.5 X 10^-4, or 1.5 ten thousandths as
strong. So, what do you do?

There is 1000 mL in the liter and 10,000 tenths of a mL in the liter.
So, one way is to make the 1.5 molar solution and take an 0.1 mL (100
uL) aliquot (portion) and dilute it to a volume of one liter.

Now, another way is to measure 1/10,000 of a mole of the dye (0.0909
grams) and dissolve it directly in one liter of solvent.

T

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  #6  
Old 07-13-2003, 02:38 AM
SNUMBER6
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Default Need help calculating Molar Concentration

>From: Tim [Only registered users see links. ]


Congratulations ... I'll give you an "A" for a High School homework problem ...

people don't arrogantly push their degrees in anybody's face ... most believe
it is wrong on many levels to do homework problems for someone ...

That should be done by the student ... and any help should come from the
teacher ... especially when no attempt at an answer was shown ... If you are so
inclined to help ... go ahead ... no one will stop you ... but if you help ...
show the way ... don't just give the answer ... and don't insult people who
disagree with doing someone's homework without showing an attempt ...
You give a man a fish ... he eats for a day ... you teach a man to fish ...


Be seeing you
In the Village
Number 6

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  #7  
Old 07-13-2003, 02:57 AM
Art
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Default Need help calculating Molar Concentration

On Sun, 13 Jul 2003 02:20:01 GMT, Tim <[Only registered users see links. ]> wrote:

OK - Now I understand! I couldn't see the relationships before or
grasp the concept of molecular weight. Thanks for explaining, Tim!
cool...
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  #8  
Old 07-13-2003, 04:01 AM
Tim
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Default Need help calculating Molar Concentration

SNUMBER6 wrote:


So, did I not provide enough explanation to have qualified as teaching?
Perhaps Art's teacher could not get the message across in
class, if in fact he is a highschool student.

You seem terribly offended. Did I strike a nerve with my grains of truth?

Is our research, publications and patents lists, and meetings more
important than taking time to teach?

T

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  #9  
Old 07-13-2003, 04:28 AM
Art
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Default Need help calculating Molar Concentration

On Sun, 13 Jul 2003 04:01:01 GMT, Tim <[Only registered users see links. ]> wrote:


Haha... No, I'm not a high school student - I am 50 years old. It's
not homework. It's a real world application using liquid dye lasers
in my work. I did take high school chemistry, and I used to know this
stuff. Just needed a refresher. If you don't use it, you lose it!
Thanks again...
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  #10  
Old 07-13-2003, 04:36 AM
Andy Hapka
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Default Need help calculating Molar Concentration

> You give a man a fish ... he eats for a day ... you teach a man to fish
....

You give a man a fish...he eats for a day...you teach a man to fish......It
gives me a good excuse to go out fishing everyday with a six pack of beer
and tell the wife i'm saving us money on groceries..???..LOL


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