[Dolphinsiu]

Under what condition, a silver metal electrode can be used to measure the concentraton of chloride ion? Explain how it works.

(I haven't studied analytic chemistry before. but how? by measuring the volume of chorine gas?)

[Borek]

Google ion selective electrodes.

[Dolphinsiu]

Yes. I have searched about ion selective electrode.

http://www.chemistry.nmsu.edu/Instrumentation/IS_Electrod.html

The solid-state electrodes(like pH glass meter) should be Ag/AgCl as it has higher ion selectivity.(But I don't know why)

What is the electrolyte inside them?

Actually why one membrane is opened in reference electrode but one membrane is closed in ion-selective electrode? Why can't be reversed?

[mdlhvn]

What is the electrolyte inside them?

It's concentrated KCl

Actually why one membrane is opened in reference electrode but one membrane is closed in ion-selective electrode? Why can't be reversed?

I dont know exactly what you mean.

In the determination of an ion by ISE, we often use two electrodes: ISE for target ion and Reference electrode (RE). Common REs are Ag/AgCl and calomen electrode. ISE contains internal RE and ion selective membrane which only allow target ion transport through.

However, I've hardly heard about chloride ISE.

[GCT]

Under what condition, a silver metal electrode can be used to measure the concentraton of chloride ion? Explain how it works.

(I haven't studied analytic chemistry before. but how? by measuring the volume of chorine gas?)

Manipulate the Nernst equation as well as the Ksp equation

Ksp for AgCl = [Ag+][Cl-]

Ag(s)-------> Ag+(aq) + e-


E=E0AgCl+(RT/nF)(log 1/[Ag+][Cl-])

substitute for [Ag+], [Ag+]=KspAgCl/[Cl-]

E=E0AgCl+(RT/nF)(log [Cl-]/KspAgCl)

But first, you are going to need to make a AgCl electrode from the Silver electrode.

[Dude]

When measuring the Cl content, a silver nitrate solution is used as the titrant.  The logic goes something like this.

1.  Initially - you have chlorine as Cl- in solution (let's say sodium chloride) and you place a silver rod electrode and a reference electrode in the solution.  The silver ion responds (primarily) to the silver content in solution and will provide a base level mV response.

2.  Middle - you start adding the silver nitrate titrant.  Chlorine immediately reacts with the silver nitrate to form an insoluble silver chloride product.  Since the product is mostly insoluble in the solution, the silver electrode will only detect a small amount of silver in solution and will change very slowly until all of the chloride reacts (silver nitrate will also react with other halogens, mercaptans and sulfides - it is not selective to the Cl anion).

3.  Equivalence point - Now all of the chlorine has reacted.  When a small amount of silver nitrate is titrated in after all of the Cl is consumed, the mV response jumps a large amount because the soluble silver nitrate is finally detected by the electrode.

4.  End - The silver electrode response range is small and will quickly saturate.  The mV will increase slowly again with the addition of more silver nitrate solution.  The overall mV versus volume of silver nitrate chromatogram will show a step change.  The middle of the step is the equivalence point or answer.

[Dolphinsiu]

Thank you to all of you! 

[kevins]

The electrolyte inside Ag electrode should be concentrated KNO3 solution.

[elmyhalily13]

Can u explain furthermore what you are trying to do with this experiment? I have done the measurement of chloride ion in liquid. It only use the titration method to measure chloride. Normally i use silver nitrate as the titrant.

[truffa]

I don't know a whole lot about chemistry but I'm looking for some help. I'm doing a project about how to measure Potassium, Chloride and Sodium out of an IV Bag. I started to look out I found that the ISE is one the best options to do it. the problem is that the concentration in the IV Bags for potassium is of 2M or 2mEq/ml ( 2*10^-3 mol/ml) and all the ISEs that I've found have a concentration range up to 1M which is half of the actual Potassium concentration. What do you recommend me to do? look for another device? or have you heard of  any ISE that could read higher concentrations of K, Cl or Na?

[enahs]

I don't know a whole lot about chemistry but I'm looking for some help. I'm doing a project about how to measure Potassium, Chloride and Sodium out of an IV Bag. I started to look out I found that the ISE is one the best options to do it. the problem is that the concentration in the IV Bags for potassium is of 2M or 2mEq/ml ( 2*10^-3 mol/ml) and all the ISEs that I've found have a concentration range up to 1M which is half of the actual Potassium concentration. What do you recommend me to do? look for another device? or have you heard of  any ISE that could read higher concentrations of K, Cl or Na?

Dilute your solution. Measure dilute solution, and correct with simple math for non-diluted solution.