hydrogen peroxide concentrations? URGENT PLEASE HELP
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hydrogen peroxide concentrations? URGENT PLEASE HELP
so, for my science fair project, i am using different concentrations of hydrogen peroxide. i bought 3% concentration of hydrogen peroxide but need 0.1%,0.5%, and 1% concentration. is there a way to add water and change the concentration? i have 25 ml of 3% hydrogen peroxide in a graduated cylinder, how much water would i need to add to get to 0.1%? 0.5%? and 1%? Please help urgent !
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agm
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Re: hydrogen peroxide concentrations? URGENT PLEASE HELP
Hi,
I moved your topic to the Physical Sciences forum where more experts will see it -- Getting Ready for the Science Fair is more about communicating your results.
There are a number of different ways of defining concentration, such as mass per unit mass (often denoted % w/w or wt%), mass per unit volume (% m/v), volume per unit volume (% v/v), etc.
http://en.wikipedia.org/wiki/Concentration
In addition, sometimes the density of a solution depends on the relative proportions of the solute and solvent (as well as temperature and pressure). Ignoring any density changes, you can think of it this way: you currently have
(N amount of X)/total content = (N of X)/(N of X + M1 of Y) = a %
and you want
(N of X)/(total content) = (N of X)/(N of X + M of Y) = b %
and you want to add M2 of Y such that M1 + M2 = M. Whether N and M are measured in mass or volume depends on how your concentration is defined.
Since you are dealing with relatively low concentrations, it is *approximately* true that the total content is equal to the amount of water (M in the equations above). Thus it is also approximately true that to change the concentration from a to b, you want to multiply the total mass or volume by b/a. By this approximation, if you want a 1% (v/v) solution and are starting with 25 ml of 3% (v/v) solution, you'll want to add 50 ml of water for a total volume of 75 ml. The correct amount is actually slightly less.
These are some of the results I got by putting "calculate concentration solution" into a search engine; you can try that, and there is likely a section on this in your science book.
http://chemistry.about.com/od/lectureno ... ration.htm
http://www.chemprofessor.com/conc.htm
http://abacus.bates.edu/~ganderso/biolo ... tions.html
Amanda
I moved your topic to the Physical Sciences forum where more experts will see it -- Getting Ready for the Science Fair is more about communicating your results.
There are a number of different ways of defining concentration, such as mass per unit mass (often denoted % w/w or wt%), mass per unit volume (% m/v), volume per unit volume (% v/v), etc.
http://en.wikipedia.org/wiki/Concentration
In addition, sometimes the density of a solution depends on the relative proportions of the solute and solvent (as well as temperature and pressure). Ignoring any density changes, you can think of it this way: you currently have
(N amount of X)/total content = (N of X)/(N of X + M1 of Y) = a %
and you want
(N of X)/(total content) = (N of X)/(N of X + M of Y) = b %
and you want to add M2 of Y such that M1 + M2 = M. Whether N and M are measured in mass or volume depends on how your concentration is defined.
Since you are dealing with relatively low concentrations, it is *approximately* true that the total content is equal to the amount of water (M in the equations above). Thus it is also approximately true that to change the concentration from a to b, you want to multiply the total mass or volume by b/a. By this approximation, if you want a 1% (v/v) solution and are starting with 25 ml of 3% (v/v) solution, you'll want to add 50 ml of water for a total volume of 75 ml. The correct amount is actually slightly less.
These are some of the results I got by putting "calculate concentration solution" into a search engine; you can try that, and there is likely a section on this in your science book.
http://chemistry.about.com/od/lectureno ... ration.htm
http://www.chemprofessor.com/conc.htm
http://abacus.bates.edu/~ganderso/biolo ... tions.html
Amanda