Australia's Science Forum

HI all,
I really hope someone is still around to help me I just got back from holidays but you hav all just started them but .
Anywho, this is probably a stupid question but can you dilute peroxide? I have a teacher asking for 3% for a year 7 practical but I only have 6%, should I just tell her to use the 6%. She want's to use it to react with a .001M solution of potassium permanganate.
Cheers

Hi Rowyrow,
All you have to do to make 3% hydrogen peroxide from 6% is just halve the strength. Add 100ml distilled water to 100ml of 6% and you have 200ml of 3% solution. It is not a stupid question, just the start of term four and adjusting to the extreme heat can put you off your game.
Lyn.

Thanks so much Lyn! Yes the heat and humidity are a bit distracting uuugh!!!

Diluting for dummies.
I have a 3% peroxide solution now I need 2%, 1%, 0.5% & 0.25%. @ 50mL of each ??????
How much 3% solution do I add to each 50mL or do I make the 2% then take out of that to get the 1% and then take out of that to get the 0.5% and so on.
This is for the prac using pureed liver that is stinking the place out right now.

Thanks in advance

I would make 100mLs of 2% (ie add 67mLs of the 3% H₂O₂ to 33mLs Distilled water), then take 50mLs of the 2% H₂O₂ and add 50mLs Distilled water to make 100mLs of 1% and just do the progressive dilutions.

3% can be bought at chemists, as can 6%. when doing dilutions I always work with the equation c1v1=c2v2 where c is concentration and v is volumn therefore in this example how much (v1) of 6% hydrogen peroxide do I need to say have 100ml (v2) of 3% hydrogen peroxide (c2):

6 x v1=3 x 100
v1=300/6
v1=50ml therefore I need to take 50ml of 6% and make up to 100ml with water to get 3%, this is a simple conversion but the equation is useful for more complex calculations, just makesure you keep your units the same on both sides of the equation MariaC

Thanks guys for the replies.

hi
This is really good website calculator, it will convert % to molarity; and from there is standard Molar dilution. Do not forget to scroll down to hydrogen peroxide in “Evaluate density of solution for” field


http://www.trimen.pl/witek/calculators/stezenia.html

Hi Estelle
Have you tried the prac using potato instead of liver?
There has been lots of discussion somewhere about this. If you search for potato you should be able to find it.
Much less mess and smell!
Julie