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# 20-Volume questions ????? OCR Chemistry watch

1. Hi,

I have a problem with this question.

Hydrogen peroxide readily decomposes to give water and oxygen.
Hydrogen peroide is sold by volume strength. For example 20-Volume H202 (hydrogen peroxide) yields 20 volumes of oxygen gas for each volume H2O2 solution.

i.) construct an equation for the decomposition of Hydrogen peroxide
I can do this part
................................ ................................ ................

ii.) Determine the concentration in mol dm-3, of 20 volume Hydrogen peroxide. Show all your working clearly.

Any one help casue i have no idea where to start.
2. (Original post by Redeyejedi)
Hi,

I have a problem with this question.

Hydrogen peroxide readily decomposes to give water and oxygen.
Hydrogen peroide is sold by volume strength. For example 20-Volume H202 (hydrogen peroxide) yields 20 volumes of oxygen gas for each volume H2O2 solution.

i.) construct an equation for the decomposition of Hydrogen peroxide
I can do this part
................................ ................................ ................

ii.) Determine the concentration in mol dm-3, of 20 volume Hydrogen peroxide. Show all your working clearly.

Any one help casue i have no idea where to start.
you didn't state unit for volume i.e cubic centimeter or litres?
3. dm^3

oh and if you want to see the question its here..

http://www.emailed.org.uk/exams/2816_1_Jan_04QP.pdf

questions 2c and 2d

thanks
4. i assume that by 20 volumes of O2 for each volume of H2O2 the question means that volume ratio of O22O2 is 20:1
therefore say that means 1dm³ H2O2 and 20 dm³ O2

1mole of O2 occupies 24dm³
therefore
20/24=0.833 moles O2

as the mole ratio O22O2 is 1:2 (1mole of O2 is produced from every 2moles of H202
there are 0.833*2=1.67moles H2O2

Concentration = moles/volume
=1.67/1
=1.67moldm-3

i'm not at all sure whether thats right but it's the best i can come up with

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