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Topic: identifying unknown sloutions  (Read 7983 times)

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chopchop

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identifying unknown sloutions
« on: April 01, 2004, 01:30:46 AM »
Six bottles have been labelled A to F.They contain solutions of silver nitrate,copper sulfate,iron(3) chloride,sodium hydroxide.sodium carbonate and hydrochloridic acid.

Devise a scheme using only these solutions to positively identify each of them.

Offline Mitch

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Re:identifying unknown sloutions
« Reply #1 on: April 01, 2004, 02:04:09 AM »
You could start by using pH paper to see which ones are acidic. Can you tell us which ones you would expect to be acidic?
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Offline AWK

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Re:identifying unknown sloutions
« Reply #2 on: April 01, 2004, 06:19:37 AM »
Lets start from blue solution (CuSO4).
After mixing separate samples of this solution with sample of each other, only in two cases precipitate will be formed, namely with NaOH and with Na2CO3.
Prepare two samples from remainded three solutions  (AgNO3, FeCl3 and HCl) and add to each sample NaOH or Na2CO3.
Only from sample Na2CO3 + HCl bubbles of CO2 will evolve indicating both HCl and Na2CO3.
White precipitate in one of other samples treated with Na2CO3 indicate AgNO3.
Brown precipitates with both NaOH and Na2CO3 indicate FeCl3
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Re:identifying unknown sloutions
« Reply #3 on: April 04, 2004, 08:01:45 AM »
Six bottles have been labelled A to F.They contain solutions of silver nitrate,copper sulfate,iron(3) chloride,sodium hydroxide.sodium carbonate and hydrochloridic acid.

Devise a scheme using only these solutions to positively identify each of them.

An alternative is to start with aq. Iron(III) Chloride. It's the yellow solution. Adding aq FeCl3 to a sample of the other solution produces varying results. White precipitate will be formed with aq. silver nitrate. Brown precipitate will be formed with aq. NaOH. Brown precipitate and effervescence of a colourless odourless gas will be formed with aq. sodium carbonate. Aqueous Copper(II) Sulphate can be identified by its blue color. The colourless solution that produce no visible change with aq. Iron(III) chloride is hydrochloric acid. Adding it to aq. Sodium Carbonate will produce effervescence of a colourless odourless gas without formation of any precipitate.
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