Hydrogen Peroxide 100 vol originally opened long time ago

Greetings to everyone,

I need to deliver a Y12 demo which needs 65ml of 2,5 M of H2O2,

The thing is that I don't want to open a brand new container we have and instead I will use an 100 vol Hydrogen Peroxide container which was originally opened about a year before.

For a new container the 100 vol H2O2 is equivalent to about 9.8M , but when it comes to an opened one?

Judging from any relative experience which should be the molarity now? (roughly)

Regards
 
What practical are you doing?
Do you have time to try this out with the opened peroxide?
The teacher is going to put a cylinder of potato in a boiling tube lidded with a bung with delivery tube which is connected to a gas syringe, I suppose she then adds the peroxide and measure the released gas in the gas syringe.
 
If you are calculating exactly, you will never get an exact result from peroxide of any age.
It is more likely that is the stated amount, but it is more important to check it actually does what you intend it to do.

edit - -pulled away from my lunch - "the propanal is not soluble in water". Shakes it a lot. Eventually dissolves. One student's test clearly has not dissolved, sample bottle must be tainted. Emptied all sample bottles and about to refill.
So finish answer with point already made!
 
Unless you are comparing results from previous investigations I'd make a solution up and see if it works okay, as long as it does and everyone gets the same solution to start with it should be okay,
 
Greetings to everyone,

I need to deliver a Y12 demo which needs 65ml of 2,5 M of H2O2,

The thing is that I don't want to open a brand new container we have and instead I will use an 100 vol Hydrogen Peroxide container which was originally opened about a year before.

For a new container the 100 vol H2O2 is equivalent to about 9.8M , but when it comes to an opened one?

Judging from any relative experience which should be the molarity now? (roughly)

Regards
Unless you are comparing results from previous investigations I'd make a solution up and see if it works okay, as long as it does and everyone gets the same solution to start with it should be okay,
I would do the same. I do it this way. I make up a 10 vol solution. Put a small amount of manganese (IV) oxide in a small side-arm conical attached to a 100ml gas syringe. Add 10ml of 10vol to the conical, place bung in top of conical and watch the gas syringe. 10 ml of 10vol should give you100ml of oxygen. I tend to write on the bottle the date I tested and the result. I have a bottle of 100vol in my fridge opened jan 2020 and 2years later it was still giving 100vol.
 
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