Dear sir
To find S, O weight percentage from EDAX spectrum. so i need 0.2 M of H2So4 solution. how much theoretical weight percentage is there?
Elie Assaf and Gert Nolze
A 1 molar solution of H2SO4 contains 98 g/L of H2SO4. So a 0.2 M solution contains 98/5 or 19.6 g/L of H2SO4 in water (in very old parlance when I was at school this would be a 0.4 N (N = Normal) solution). Obviously this is 1.96 weight percent in water but I don't think that this is what you mean by your question. We note that you would have to dilute concentrated acid (always add acid to water not the other way around) in order to get a 0.2 M solution. If you buy in a 1 M solution then life is easy (assuming no volume changes on mixing), 100 mL of the 1 M solution would be made up to 500 mL with (approximately) 400 mL of distilled water. A bottle of concentrated sulfuric acid is 98% with a density of 1.84 g/cm3 and a molarity of 18.4M. If you dilute this to 0.2 M then your finished density would be close to water. If, for example, you want to make 100 mL of 0.2 M H2SO4 from concentrated acid (98% as before) then the calculation is easy: V = (100*0.2)/18.4 = 1.09 mL of concentrated acid made up to 100 mL with DI water. This would not be easy to do in practice - you could weigh out 1.09*1.84 ~ 2 g of H2SO4 and dilute to 100 mL. Personally I'd pipette out 1 mL make up to 100 mL and use an acid-base titration to measure the exact molarity (~ 0.18 M) as almost certainly this concentration would be 'fit for purpose'.
Is there no teacher or lecturer at university that can deal with this simple stuff?
I wondered who Gert Nolze and Elie Assaf were in the original question! Now I know....
Guten Abend, Gert!
Now I have one from two. Come on Elie, where are you?!
EDAX - EDS? Energy-dispersive X-ray spectroscopy?
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