How Does a pH Meter Work and What Role Does the Reference Electrode Play?

[Mizuki168]

Hey guys, so I have a project on the pH meter. Basically on what it is, what it's used for, how it works, and what principles does it run on. It is a group project but we can't seem to figure out some points and we've become very confused!

Mainly, it's how it works. We researched and understood that the pH meter has electrodes and it kind of works like a thermacouple thermometer. There are 2 electrodes (a pH electrode and a reference electrode). The pH electrode, according to us, is a glass electrode that has a membrane made out of some metal. When the glass electrode is put in the tested solution to determine the pH level, the hydrogen ions go in the glass electrode and then in turn some metal ions from the membrane go into the solution? And then there is a electric potential difference that is sent to the voltmeter that helps convert it into pH units.

But out real problem is, is what use is the reference electrode. We've done a lot of research on it and everywhere just says that it's to provide a stable electric potential. But how? And why?

 

[Borek]

www.ph-meter.info[/url] and specifically [url=http://www.ph-meter.info/pH-electrode-construction]www.ph-meter.info/pH-electrode-construction[/URL] contain most of the information you need.

Reference electrode is usually Ag/AgCl electrode, not different from those routinely used as a reference in many electrochemical experiments.

 

[Mizuki168]

www.ph-meter.info[/url] and specifically [url=http://www.ph-meter.info/pH-electrode-construction]www.ph-meter.info/pH-electrode-construction[/URL] contain most of the information you need.

Reference electrode is usually Ag/AgCl electrode, not different from those routinely used as a reference in many electrochemical experiments.[/QUOTE]


Thank you for the websites however even after reading them I'm not quite understanding anything about the reference electrode...

 

[Borek]

I am not sure what the problem is. Such an electrode is made of Ag wire covered with AgCl, submerged in solution of chlorides of known concentration (usually either 1M or saturated KCl). Its potential is constant because that's the way electrodes work - this particular electrode has potential depending on the concentration of chlorides, as long as this concentration is constant, potential is constant as well.

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[Mizuki168]

Oke...so the chloride stays in the reference electrode. Then why must it be dipped in the solution being tested for pH level?

 

[Borek]

Not sure what your question is. Why whole electrode must be dipped? You can't measure concentration remotely. Why reference electrode must be dipped? You have to close circuit, you are measuring relative potential.

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