# Chemical Forums

## Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: angelguy on June 16, 2005, 08:47:36 AM

Title: Determinig the ion concentration in solution
Post by: angelguy on June 16, 2005, 08:47:36 AM
Hi all,

System :
I have a solution of different salts such as CaCl2,MgSO4,NH3H2PO4,KCl, NaCL,Glycerol and so on. As we all know this salts will dissociate in their corresponding ions.
Also I have to add CO2 in the solution(but not sure about it). And can maintain its pH by adding acid or base.

Question:

I need to determine the concentration of all this ions formed. Since I have no idea about anaytical chemistry, sorry to ask you this silly question.

Angelguy

Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 16, 2005, 08:51:42 AM
I really dunt have any idea about analytical chemistry so please make me understand in simple terms.I will be very thankful to each reply and comments on this.

angelguy
Title: Re:Determinig the ion concentration in solution
Post by: arnyk on June 16, 2005, 05:08:07 PM
Are you adding all those into a single solution?  It doesn't matter anyways I don't think...all you need to know are the amount (moles) of each salt you have in solution.  Then figure the moles of the specific ion in each salt (for every 1 mole of the salt, how many moles of the ion will there be?).  For [] you would also need the total volume of the solution.

For example: I have 3 mol of KBr, and 5 mol of K3PO4 in a 10L solution.  What is the [K+] in solution.

For every 1 mol of KBr, I also have 1 mol of K+ ions.  Therefore, there will be 3 mol of K+ in 3 mol of KBr.

For every 1 mol of K3PO4, I have 3 mol of K+ ions.  Therefore, there will be 15 mol of K+ in 5 mol of K3PO4.

Add the moles together of the K+ ions: 3 + 15 = 18 mol of K+ ions in solution.

[K+] = n/V
= (18)/(10)
= 1.8 M

Now do that, except with all of those salts you have there.
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 16, 2005, 09:30:58 PM
hey.. thanks for your reply however, I am done with that stiochionetry thingy.

My object is , I have the known pH of the solution and therefore i have known H+ content and will maintain the same content, evenif there is changes in the H ion concentration, by adding acid or base.
Therefore< i have determined the concentration of all the ions theretically. I need to verify my results by doing actualy experiment. I hope you will understand what i mean.

I have taken certain steps in doing the stuff. Please let me know if i am in right direction.

2). Or forming MgOH2 precipitate( but i think this will not be in significant amount to hold in the filter paper) :) Please let me know the expert advice in this.

Thanking you once again and hoping for similiar response.

Angelguy
Title: Re:Determinig the ion concentration in solution
Post by: asqa on June 17, 2005, 04:53:35 AM
if you titrate against EDTA you will get total hardness(Ca+Mg) but if you make the solution as hydroxide Mg forms Mf(OH)2 it will not give response to EDTA if you use calcon indicator.
but in your question you want to know the conc. of ions. so what should you do is, you find the anion and cation conc sepaerately and convert it to corresponding salt.
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 17, 2005, 07:14:25 AM
Could you please extend on how can i determine the anion and cation concentration and thereby correponding salts? Actually, I am not analytical chemistry person..  :)

Actually, I tried adding EDTA assay in the Cacl2 and MgSO4 soultion and figure out that it forms the white precipitate in larger amount. And I think, I need to change my approach. And the method you suggested seems very feasible.

Thankyou

Ashish
Title: Re:Determinig the ion concentration in solution
Post by: Borek on June 17, 2005, 07:18:07 AM
What is a purpose of the whole experiment? Analysis? Equlibrium determination? I don't get it.
Title: Re:Determinig the ion concentration in solution
Post by: asqa on June 17, 2005, 07:22:15 AM
what do you want exactly? i am not clear
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 17, 2005, 07:24:14 AM
actually, I figured out the concentration of the ions by calculation @ different pH and want to verify my results by experimenting the media.

Thanking you

angelguy
Title: Re:Determinig the ion concentration in solution
Post by: asqa on June 17, 2005, 07:35:14 AM
actually, I figured out the concentration of the ions by calculation @ different pH and want to verify my results by experimenting the media.

Thanking you

angelguy

dear asish,

if this is the case find out the cation/anion content by separate experiment.Then convert it by caculation as salt.

when doing a calculation of chloride content put equivalent weight of calcium chloride instead of chloride equivalent weight

eg. titre value X strength of silver nitrateX EQ. weight of calcium chloride/volume of sample

jope that its help u
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 17, 2005, 07:50:19 AM
I dunt think i got it. However, Could u please explain me as in how do I actually perform the lab and calculation to be done after getting results.  ???

Lemme give you brief idea :

1). I have a media which i am preparing be adding the known amount of all the salts one after another. ok

2). I can also maintain its pH by adding acid or base in it.

3).I have a calculation center program which compute the ion concentration theortically. I wanna test thid program for its accuracy.

I case you wanna know wht salts i have. Here you go,
1). Cacl2,2H20 2). MgSO4 , 3) Nh4H2PO4 4)Kcl 5) Nacl 6). Glycerol..

angelguy
Title: Re:Determinig the ion concentration in solution
Post by: asqa on June 17, 2005, 08:06:38 AM
I dunt think i got it. However, Could u please explain me as in how do I actually perform the lab and calculation to be done after getting results.  ???

Lemme give you brief idea :

1). I have a media which i am preparing be adding the known amount of all the salts one after another. ok

2). I can also maintain its pH by adding acid or base in it.

3).I have a calculation center program which compute the ion concentration theortically. I wanna test thid program for its accuracy.

I case you wanna know wht salts i have. Here you go,
1). Cacl2,2H20 2). MgSO4 , 3) Nh4H2PO4 4)Kcl 5) Nacl 6). Glycerol..

angelguy

Firstly go for total hardness test.it will give the content of Ca+Mg.Then go for Ca hardness it will give Ca content.Then substract Ca from total hardness you will get Mg.Go for phosphate test, it will give the phosphate content.Go for chloride test it will give total chloride of Ca+k+Na.substract the Ca& K you will get Nacl.finally test for glycerol
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 17, 2005, 08:24:35 AM
Thanks a bunch now things are making sense to me.

But cud u just breeze through,  how do I do all of these test. Sincerely , I dunt any idea about analytical chemistry and I am not chemistry major either. Please give the order at which i shud start doin the tests. And how much media do i prepare all thoose stuff.

Thanking you

angelguy
Title: Re:Determinig the ion concentration in solution
Post by: asqa on June 17, 2005, 09:41:22 AM
you do the what ever conc(preferrely low concentration) and do the order of  test  what i mentioned earlier.But if your pH of solution is more acidic or more basic you have to do some prework before analysing
Title: Re:Determinig the ion concentration in solution
Post by: angelguy on June 17, 2005, 09:53:27 AM
I can get done with the calcium and phospate test. But i am still confused regarding predicting Ca++ and Mg++. That will be kind enough if you can give me the procedure of determining these contents :)
Also the calculation behind it.

Also I can use watever pH I want because i have the model which will determine the concentration of all the ions.Please guide me as in wat pH will be good.

Thanking you

angelwire
Title: Re:Determinig the ion concentration in solution
Post by: Borek on June 17, 2005, 10:53:19 AM
It still doesn't make sense to me.

Quote
I have a media which i am preparing be adding the known amount of all the salts one after another.

If you know amount of salts added, water hardness masurement doesn't make sense - what you will get is the concentrations of ions put into the solution +/- experimental error. Analysis is just a waste of time.

If you are after equlibrium concentrations, analysis of total concentrations (as in the case of water hardness) will not give you any answer. Equlibrium concentrations can be measured using specroscopic or potentiometric techniques mainly.
Title: Re:Determinig the ion concentration in solution
Post by: arnyk on June 18, 2005, 10:16:00 PM
^That's true...if all you're after are the ion concentrations then all you need to know is the amount of each salt added and the total volume of solution.
Title: Re:Determinig the ion concentration in solution
Post by: carl_pitt on August 20, 2005, 10:02:36 AM
i think you can use potentiometry in low ph