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Need some Chemistry Help

Im currently doing my titration AS chemistry coursework(OCR) here is the question:

I have been provided with 250cm3 of a solution which has been made such that it contains approximately 2.5 g dm-3 of calcium hydrogen carbonate. Also available is nitric acid , which has a concentration of exactly 2.00 mol dm-3 the acid is to concentrated and I will need to dilute it.
I have to plan an experiment which will allow me to determine the concentration in mol dm-3 of the calcium hydrogen carbonate in the solution as accurately as possible. I am allowed to use normal laboratory apparatus and indicator solutions are available I may not use any other chemicals.


I dont no which indicator to use for the titration either: methyle orange or phenolphthalene. which 1 shall i use and y
Reply 1
Avatar for oxymoron
oxymoron
7
to decide on indicator: think about if it is a strong/weak acid and base and look up the pH ranges over which the indicators change colour. (Look up titration curves as well).

To plan the experiment, I would suggest: work out the approximate concentration of the calcium hydrogencarbonate, and dilute the acid down to approximately the same concentration. Titrate 25cm^3 aliquot of acid using a burette. From this you should be able to work out the concentration of base using the exact conc of the acid.

Hope that gets you started.
Reply 2
Avatar for oxymoron
oxymoron
7
you may also find this site useful

http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html

(look especially at the bottom of the page)

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