[mass]

Solution S was prepared by dissolving 5g of sample in 100ml h20. 10ml of solution s was diluted to 15ml with h20. This was then added to 1ml of 25% w/v barium chloride solution and the opalescence obtained was no greater than when 15ml 10ppm sulphate solution was added to 1ml 25%w/v barium chloride solution. Calculate max amount of sulphate present in sample.

Where do i even start on this?

[DrCMS]

It's just simple maths.

[Arkcon]

Try to break it apart.  There is a standard, the second mixture.  There is a detector, integrator and quantification system, the eyes and brain of the human observer.  You simple have to determine, like DrCMS: said, what quantities are associated with the serial dilutions.

[mass]

It's just simple maths.

Well can you please take me through it step by step, atleast then I will get what to do.


Does anyone know which undergraduate chem book, these type of questions can be found in as I want to have a go at more.

[Arkcon]

I suppose, it is in many, if not all such textbooks.  I don't know if there's a web page dedicated to this sort of thing ...

Try to work with the second part, to start with.  It says the unknown sample's turbidity "is no greater than"  and then asks for "the maximum" value. If it had instead said, "the unknown gives a spectrophotometer reading of exactly 0.1000, and the 10 ppm standard solution gives a spec reading of exactly 0.1000", wouldn't you know what to do?

For an example of an old post on this forum, where this procedure had to be done, repeatedly, to solve the problem, check out this old post:

http://www.chemicalforums.com/index.php?topic=25535.0

These sort of questions come up often on this board, working with concentrations can stymie even experienced chemists.  Try to practice the basics some more, until it becomes second nature.

[mass]

I suppose, it is in many, if not all such textbooks.  I don't know if there's a web page dedicated to this sort of thing ...

Try to work with the second part, to start with.  It says the unknown sample's turbidity "is no greater than"  and then asks for "the maximum" value. If it had instead said, "the unknown gives a spectrophotometer reading of exactly 0.1000, and the 10 ppm standard solution gives a spec reading of exactly 0.1000", wouldn't you know what to do?

For an example of an old post on this forum, where this procedure had to be done, repeatedly, to solve the problem, check out this old post:

http://www.chemicalforums.com/index.php?topic=25535.0

These sort of questions come up often on this board, working with concentrations can stymie even experienced chemists.  Try to practice the basics some more, until it becomes second nature.

Any good specific textbooks which spring to mind?

[Arkcon]

Any good specific textbooks which spring to mind?

Well, I'd start with a general chem text, at the very beginning, before they even start to teach chemistry, to learn how these sorts of word problems, become calculations.  I'm thinking an analytical chemistry text, would also be a richer source for these sorts of calculations, at the beginning.  See what the university uses for such a class, as to borrow the text from a prof, or from the library.

[Arkcon]

Oh look, some one else is working on a similar problem today.  http://www.chemicalforums.com/index.php?topic=32229.0;topicseen  Maybe that thread has some hints for you.

[mass]

I am still having the same problems. Been at it for a long time and don't even know where to start.