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Topic: Chemistry problem  (Read 15197 times)

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Offline ganz

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Chemistry problem
« on: May 23, 2006, 06:40:02 PM »
Hi, Im having trouble trying to solve this problem and im not sure how to start it.

A solution is prepared by dissolving 10.00 grams of a monobasic salt in a total volume of 1.00 litres.  The pH of the solution was measured at 13.07 and a conductivity experiment determined that this salt was completely ionized in solution.  What is the molecular weight of this monobasic salt?
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Offline wereworm73

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Re: Chemistry problem
« Reply #1 on: May 23, 2006, 07:29:10 PM »
Since your monobasic base is 100% ionized, one mole of it will react completely with one mole of H+.  So, you just need to find out how many moles of H+ (from the water) reacted when the base was added.  That will give you the number of moles of your base.  Once you have that number, you can get grams/mole for the molecular weight.
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Offline ganz

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Re: Chemistry problem
« Reply #2 on: May 23, 2006, 08:17:37 PM »
Thanks for the help but im not sure how to find either of those could you please show me step by step?

Thank you
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Offline mike

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Re: Chemistry problem
« Reply #3 on: May 23, 2006, 08:27:42 PM »
pOH = -log10[OH-]

[OH-] = ____ mol.L-1

v = 1.00L

and

m = 10.00g

using:

n = m/M

and

c = n/v

you should be able to work it out..
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Offline champ

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Re: Chemistry problem
« Reply #4 on: January 17, 2008, 08:14:12 PM »
is the answer for this quesion is 0.77g/mol or somthing else..??? please need help here!!!!!!!!!!!
 please correct me  thanx .
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Offline Borek

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Re: Chemistry problem
« Reply #5 on: January 18, 2008, 03:19:49 AM »
Quote from: champ on January 17, 2008, 08:14:12 PM
is the answer for this quesion is 0.77g/mol or somthing else..??? please need help here!!!!!!!!!!!
 please correct me  thanx .

For sure more than that, lightest possible substance - atomic hydrogen - has molar mass of 1 g/mole. Base must have at least about 23 g/mol (LiOH).
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Offline AWK

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Re: Chemistry problem
« Reply #6 on: January 18, 2008, 07:22:51 AM »
Quote from: champ on January 17, 2008, 08:14:12 PM
is the answer for this quesion is 0.77g/mol or somthing else..??? please need help here!!!!!!!!!!!
 please correct me  thanx .
Explore hint of mike.
Calcutate correctly pOH then [OH-]
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Offline champ

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Re: Chemistry problem
« Reply #7 on: January 18, 2008, 11:23:55 AM »
what will be the rite answer???? Please help me here??? thanxx 
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Offline AWK

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Re: Chemistry problem
« Reply #8 on: January 18, 2008, 11:45:13 AM »
Between 70 and 100.
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Offline DigiTan

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Re: Chemistry problem
« Reply #9 on: January 19, 2008, 03:26:41 AM »
I also got a small molecular weight from this and arrived at 1.16 grams/mole.  What do you do after you calculate the moles of hydroxide?

[edit]
Okay, disregard that.  I just got something in AWK's range.  Be sure to double-check your minus signs while dealing with the the LOG and 10x terms.
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Offline champ

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Re: Chemistry problem
« Reply #10 on: January 19, 2008, 10:01:53 AM »
Is the Answer for this question "85.11g/mol".?.. thats the rang AWK told me ... if i am wrong then please correct me... it will be highly appreciated.. thank you very much..
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Offline Borek

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Re: Chemistry problem
« Reply #11 on: January 19, 2008, 10:59:31 AM »
Seems OK.
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Offline DigiTan

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Re: Chemistry problem
« Reply #12 on: January 19, 2008, 01:47:42 PM »
Same as what I got.  What exactly is a monobasic salt?  Do they always make total dissociation in water or does that name have some other meaning?
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Offline champ

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Re: Chemistry problem
« Reply #13 on: January 20, 2008, 06:57:23 PM »
it might help but i am not suhttp://www.freepatentsonline.com/4647392.htmlre..
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Offline DigiTan

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Re: Chemistry problem
« Reply #14 on: January 20, 2008, 08:05:55 PM »
It didn't really explain what a monobasic salt is, only that one is used.  99% percent was organic chemistry I haven't even gotten to yet.

Does "monobasic" have some relationship with "monoprotic."  They sound like opposites, but I hear them described as having the same meaning.
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