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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: xstrae on June 24, 2006, 11:57:39 AM

Title: Volume Strength
Post by: xstrae on June 24, 2006, 11:57:39 AM

Can someone explain what volume strength is and how to find the volume strength of a given compound?
The question is : Determine the  volume strength of 1.5 N H₂O₂

thanks! :)

Title: Re: Volume Strength
Post by: xstrae on June 25, 2006, 11:26:01 AM

hey i read somwwhere that the volume strength of a compound is equal to number of times its volume of O₂ at STP on decomposition. is that true?? ???

Title: Re: Volume Strength
Post by: Stewed_ant on June 25, 2006, 12:43:30 PM

This is the first time i heard of volume strength !   :-\  So the following explanation will be the best i can do!  ??? :-[

This is what i found on a website.

"Concentrations of hydrogen peroxide solutions are sometimes quoted in molarity, more often in "volume strength." Volume strength is unique to hydrogen peroxide. When hydrogen peroxide decomposes it is converted to water with the liberation of oxygen gas. One litre of "10 volume" hydrogen peroxide will produce 10 litres of oxygen when it decomposes; and one litre of "5 volume" hydrogen peroxide will produce 5 litres of oxygen. So it is simply a convenient way of expressing the solution's strength. But remember that hydrogen peroxide solutions are not stable and decompose easily so that what has been bought as " 10 volume" does not stay at that strength for long."

http://palimpsest.stanford.edu/waac/wn/wn12/wn12-3/wn12-306.html

This means that since 2H2O2 --> 2H2O + O2 , if you have a litre of a "10 volume strenght" hydrogen peroxide decomposing, your'll get 10 litres of oxygen etc...

Which begs the question, why are they asking for the volume strength of H2S04 when it's meant to be only used for peroxide???

In any case maybe we can apply, the same sort of thing, find the equation for decomposition of H2S04.

(balance)H2SO4 ----> Something + (balance) O2

For GAS, (NOT LIQUED)
N.o. Moles = Volume at S.T.P/22.4 (or was it 24.5 at 20 degrees celcius be sure to check that).

get the volume of H2S04,  then find the moles/volume of 02 at STP according to the equation. And the ratio to the volume of your O2 to your H2SO4 will be your volume strength.

P.S. I don't know if i can personally do this question personally, but hopefully this will get you closer to figuring out how, if you do figure it out, PLEASE LET ME KNOW THE SOLUTION!!!

Title: Re: Volume Strength
Post by: xstrae on June 25, 2006, 01:46:05 PM

First of all, my apologies for typing the question wrongly. The actual question was related to H₂O₂. sorry! :-[

ok i managed to work it finally! here goes
1.5N H₂O₂ = 0.75 M H₂O₂.
There 1 litre of the solution contains 25.5g H₂O₂.  (0.75 * 34)
According to the equation,
                   2H2O2 --> 2H2O + O2
68g H2O2 gives 22.4 litre O2
25.5g H202 gives 8.4 litres, which is the answer given in my book.
therefore the volume strength of 1.5 H202 is 8.4.  :)

thanks stewed.. it clicked only after reading your explanation.  ;D