Molarity of 20 volume hydrogen peroxide Watch

raffles
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Does anyone know what the molarity of 20 volume hydrogen peroxide should be, roughly? Would be very helpful, thanks
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Eau
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Huh?

This is an impossible question.

There is not a molarity any solution should be.
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oceane
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(Original post by catty p)
Does anyone know what the molarity of 20 volume hydrogen peroxide should be, roughly? Would be very helpful, thanks
20 volume means 1dm3 of the H2O2 solution will produce 20dm3 of oxygen, where:

H2O2 -> O2 + H2:

i.e 1:1 stoichiometry. At 298K and 1atm pressure, 1 mole of gas occupies 24.45dm3. So 20/24.45 = 0.818 mol. O2 produced, which means there were 0.818mol H2O2 in 1dm3. Therefore molarity is 0.818M at 298K.
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cowsgomoo
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no thats not right!!

the equation is 2H2O2 (aq) --> 2H2O (l) + O2 (g) for a start.

Hydrogen peroxide 20-volume solution contains 6% H2O2 (i.e. 60g of H2O2 in 1000g of solution). Mr of H2O2 = 34gmol-1. Therefore the concentration of 20-volume solution is about 60 ÷ 34 = 1.76moldm-3.
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abcd1234abcd
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(Original post by cowsgomoo)
no thats not right!!

the equation is 2H2O2 (aq) --> 2H2O (l) + O2 (g) for a start.

Hydrogen peroxide 20-volume solution contains 6% H2O2 (i.e. 60g of H2O2 in 1000g of solution). Mr of H2O2 = 34gmol-1. Therefore the concentration of 20-volume solution is about 60 ÷ 34 = 1.76moldm-3.
Hi could you help me please? This question is the same as an exam question I'm doing: determine concenrtation of 20 volume H202

I've looked at the mark scheme but don't understand all the steps, the first is dividing 20 by 24 to find the moles of 02 produced, which is 0.83 moles.
But then they next multiply this answer by 2 to get the answer of 1.67 mol dm^-3
I don't understand this last step, I'm guessing it has something to do with the 2:1 ratio between 02 and H202 but also how can the value in moles suddenly become a concentration?
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Plato's Trousers
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(Original post by abcd1234abcd)
Hi could you help me please? This question is the same as an exam question I'm doing: determine concenrtation of 20 volume H202

I've looked at the mark scheme but don't understand all the steps, the first is dividing 20 by 24 to find the moles of 02 produced, which is 0.83 moles.
But then they next multiply this answer by 2 to get the answer of 1.67 mol dm^-3
I don't understand this last step, I'm guessing it has something to do with the 2:1 ratio between 02 and H202 but also how can the value in moles suddenly become a concentration?
right.

2H_2O_2 \rightarrow 2H_2O + O_2

so we know 2 moles of hydrogen peroxide produces 1 mole of oxygen.

"20 volume", means 1 dm3 of peroxide solution produces 20 dm3 oxygen.

20 dm3 oxygen is 20 / 24.47 = 0.817 moles (at 298K and 1 atm)

therefore, 1 dm3 of solution must contain 2 x 0.817 = 1.635 moles peroxide.

so "20 volume" hydrogen peroxide is 1.635M
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Tuckersluck
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Where are you getting 24/24.47 from?!
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Borek
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Not 24/24.47 bout 20/24.47. 20 (dm3) is the volume of oxygen produced (thats what "20 volume" means), 24.47 dm3 is the volume of one mole of ideal gas at STP. 20/24.47 is number of moles of oxygen produced.
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charco
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(Original post by Borek)
Not 24/24.47 bout 20/24.47. 20 (dm3) is the volume of oxygen produced (thats what "20 volume" means), 24.47 dm3 is the volume of one mole of ideal gas at STP. 20/24.47 is number of moles of oxygen produced.
I imagine that the 'volume' measure refers to room temperature ...

... I don't know this for a fact, but it would seem more likely in a household solution.
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Borek
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Yes, perhaps more like RTP or SATP. Whatever.
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Plato's Trousers
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(Original post by charco)
I imagine that the 'volume' measure refers to room temperature ...
24.47 dm3 per mole is at 298K and 1 atm.

298K is room temperature (at least in my house).
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purplets7
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The reason why it "suddenly becomes a concentration" is because you take the moles (1.67 mol dm^-3) and divide it by the volume of hydrogen peroxide (1 dm3) to get the concentration! So since you're only dividing by 1, the number stays the same, and you can change the units!!
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Shumaila l
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(Original post by cowsgomoo)
no thats not right!!

the equation is 2H2O2 (aq) --> 2H2O (l) + O2 (g) for a start.

Hydrogen peroxide 20-volume solution contains 6% H2O2 (i.e. 60g of H2O2 in 1000g of solution). Mr of H2O2 = 34gmol-1. Therefore the concentration of 20-volume solution is about 60 ÷ 34 = 1.76moldm-3.
How do we know it has 6% H2O2?
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sahil2832
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1.78
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123iron123
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The volume of H2 O2 and its strength numerical
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Rauviji1006
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Hi, without getting into equatuons can somebody tell me how much% is 20 volumes of H2O2? I am looking for 3% H2O2 and there is no mention of% in any bottle. Only that it is 20volumes. Thanks.
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