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Topic: NEED HELP IN SYNTHESIS CALCULATION.  (Read 4917 times)

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Offline Perdesi

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NEED HELP IN SYNTHESIS CALCULATION.
« on: November 02, 2008, 12:13:11 PM »
I need your help to understand this problem. I tried using different ways but could not solve it.
 
Protocol:
In a synthetic reaction 6 gm (25.9 mmol) Glutamic acid benzyl ester (MOL. WT: 237.25) was treated with 45 ml of 1N HBr (46 mmol).
 
Problem:
What I have is 48% HBr. How much should I need to treat with 5Gm of Glutamic acid benzyl ester?
 
 
I hope SOME ONE CAN help me.
Thanks in advance.

Offline Arkcon

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Re: NEED HELP IN SYNTHESIS CALCULATION.
« Reply #1 on: November 02, 2008, 12:25:45 PM »
Can you convert 48% HBr to the units of molarity (M)?  The rest of your question is personal information not germane to the problem.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Perdesi

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Re: NEED HELP IN SYNTHESIS CALCULATION.
« Reply #2 on: November 02, 2008, 02:38:38 PM »
Still unable to solve it. The HBr solution is 40% W/V.

Offline Arkcon

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Re: NEED HELP IN SYNTHESIS CALCULATION.
« Reply #3 on: November 02, 2008, 04:14:43 PM »
Still unable to solve it. The HBr solution is 40% W/V.

Great, that was a question I had, was it w/v or w/w or v/v.  Now, what does 40% HBr w/v mean?  What does the abbreviation stand for?  How would you make it, for your self?  And how would you make, what you need 1 N HBr, from scratch, for yourself?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Perdesi

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Re: NEED HELP IN SYNTHESIS CALCULATION.
« Reply #4 on: November 02, 2008, 08:20:17 PM »


I tried to solve it as: please inform me with my mistake  ???, which is there..
Thank you again.
Here I tried to solve it. What I need actually a 37.5ml of 1N HBr.

What I have is 48% HBr. 40%W/V , density 1.49, mol wt: 80.92
(Fluka - cat # 18710)

So I calculated first the  molarity as:

48 gm HBr in 100 ml of solution (that means my solute is 48 gm & solvent is 52 ml.

(%/mol.wt)/lit of solvent:

48/80.92= 0.593 moles

Molarity=0.593 moles/0.052 = 11.40 molar

that means my HBr bottle have 11.4M solution....(I am hoping it is correct)

Now coming back to my orignal question, i.e., I need 37.5ml of 1N HBr.

Since for HBr, 1M = 1N.

using C1V1 = C2V2.

 1M x 37.5 = 11.4 x V1

V1 = 3.28 ml

I will take 3.28 ml of 48% HBr & make up a solution of 37.5 ml

Please inform me if I am doing OK....at least I tried, but still not sure.

Regards,

MN


Offline Arkcon

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Re: NEED HELP IN SYNTHESIS CALCULATION.
« Reply #5 on: November 03, 2008, 09:24:46 AM »
that means my HBr bottle have 11.4M solution....(I am hoping it is correct)

If this is an actual bottle, for an experiment you intend to do, the molarity is most likely on the label.  If you're allowed to check it before you start working, you should.

Quote
48 gm HBr in 100 ml of solution (that means my solute is 48 gm & solvent is 52 ml.

You make an assumption here, that I don't think you should (I may be wrong about that.)  Apparently, you suspect the same, that's why you mentioned the density of the hydrobromic acid solution.  Have you heard of something you have to do here, somewhere before?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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