Voltameter & Sulfuric Acid

[Labbie]

We have used a Voltameter with of course Sulfuric Acid Conc, we have new plugs at the bottom. It took a long time for it to bubble this time around, although the plugs do not fit too well, just a little lose, (Sulfuric acid drips out). Could our Sulfuric acid be too old, it was purchased in 1997, has been kept in amber glass bottles, in a cool dark place since then.

How long is the self life for Sulfuric Acid Conc

Any other tips that could help us????????????????

How do other people do this experiment??

[lada]

I never use conc sulfuric acid. I use 1-2M. It works very well. Good luck
Lada

[Robdean]

Yes we use 1M sulfuric acid here too. It works well without any problems encountered as yet.
Be careful cleaning up the dripping conc acid!!!

[Labbie]

The teachers here like to use Sulfuric Acid of course with distilled water. Perhaps their judgement of how much Conc sulfuric acid they put in is the problem??

[Lyn]

Sue,
I have never used more than a 2M H2SO4 solution for the voltameter. The use of 1M H2SO4 is also suitable. The amount of reaction depends on the setting of the power pack. I have never had a problem getting results. Personally I would never use Conc H2SO4 with this equipment. I think that is way over the top. However if the reaction was not going well a few mls of Conc added with a plastic pipette can speed up the reaction.

Lyn.

[hel]

We actually use 0.1M Sulphuric acid. Never had a problem with the reaction. I definately would not use conc. Sulphuric acid, too many hazards & wear & tear on equipment. Good Luck

[kimmy]

We only ever use between .5M and 2 M acid for this. I never let the concentrate go out for student pracs. The teachers may use them for demonstration but that is all to many hazards with giving students concentrates we avoid this whenever possible.

[Labbie]

The students never use Conc Sulfuric Acid. It was only a Demo by the teachers.

[JudyM]

Instead of using sulfuric acid I use 0.5 or 1M sodium sulfate and a few drops of universal indicator soln.

Add the sulfate and universal indicator before you fit the electrodes, then fill from the top as usual. Shows pH levels at each electrode and so far I've found this way works well.

Cheers

[Labbie]

Great Tip Judy, Thanks

[Ian]

Similarly, I use 1M in the bottom and then put water on top. It works well.
The leaky electrodes are a worry. My electrodes are in small Rubber stoppers, which can be pushed in tighter to make a better seal if they leak.

I think that this is one of those dem's that always works better for the Lab Assistant than it does for the teachers! We need dem's like this just to maintain our level of respectability! The other one that I specialise in is setting up the CRO. NOBODY else can do that!

Regards
Ian

[Ocean Breeze]

Sue
Forgive me if I am asking the obvious.. ....
I wasnt sure if you meant that
you filled the voltameter completely with conc H2 SO4, or that you filled the voltameter with water and then added some conc H2 SO4.

My thinking is that the acid is only used to assist the reaction electrically for the water to break down. So if theres not much water in your voltameter that could be a problem.

I fixed my leaking voltameter using some new rubber tubing and silicone sealant. Failing that you can buy replacement electrodes from places like Serrata

[Labbie]

Hi, I purchased Electrodes new earlier this year, they do not fit very well, one side leaks. They are of the rubber style. The teachers like to do, it them selves, I guess they put the water in first, then add the conc Sulfuric Acid. Even by pushing the rubber electrodes up it still leaks. I really do thank you for all your help. I guess we may have to purchase a whole new one??

Regards

[Ocean Breeze]

Hi Sue
My suggestion with the acid is that you dont allow the teachers to use the conc acid. Provide them with a litre bottle of dilute sulfuric acid to fill the unit- between 0.5 M and 2 M.

If money isnt too tight, as you say, just buy a new one. Remember to keep the platinum from the electrodes! Theyre worth quite a bit!