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Specialty Chemistry Forums => Chemical Education and Careers => Topic started by: Borek on April 05, 2005, 06:41:16 PM

Title: mixing solutions
Post by: Borek on April 05, 2005, 06:41:16 PM
Hi All,
 
I am trying to find some web based resources on the calculations of concentrations when mixing known solutions (like "what you get when you mix 100 mL of 5% NaOH with 50 mL of 20% NaOH"). As for now I am finding only pages about dilutions (which is basically a particular case of mixing solutions - just one concentration is 0).
 
I know how to do the calculations, what I need is some examples of English terms used in questions and in calculation descriptions.
 
Either I am using wrong keywords in google or such things are rarely taught now  >:(
Title: Re:mixing solutions
Post by: Mitch on April 06, 2005, 03:11:21 AM
I think your question might be to basic for there to be an English guide.
Title: Re:mixing solutions
Post by: Borek on April 06, 2005, 05:16:30 AM
I don't know...

Thirty second googling and you have scores of courses on molarity, molality, % concentration, molar fractions and so on, together with tons of questions "How much calcium sulfate is needed to make 100cm3 of 0.25M CaSO4?" or similar. But I was not able to find a single question on the mixing of solutions - and that is not a question that is more basic that molarity definition. In fact when I was a student it was a thing that was taught last...

AWK, are you still teaching 'regula krzyzowa'?

Funny thing, I have tried to search for 'cross-rule' and I have found references to it on Bulgarian and Czech pages only...
Title: Re:mixing solutions
Post by: savoy7 on April 06, 2005, 06:15:06 AM
In my experience, secondary and post-secondary chem education in the US does not address the mixing of solutions as a separate topic in the solution units.  Usually, we add some problems based on it.

For example, here is an AP (advanced placement) Chem Site that has a few problems based on the idea.  No notes are provided on how to complete the problem.  
http://dbhs.wvusd.k12.ca.us/webdocs/Solutions/Dilution.html

I guess I view the topic as a basic one once the student understands concentration.

Title: Re:mixing solutions
Post by: GCT on April 13, 2005, 09:50:10 AM
All you'll need to know is the chemical terms, molarity, concentration, etc...from the individual concentrations, convert to moles

(sum of the moles)/(sum of the volume)=new concentration