April 23, 2024, 07:28:08 PM
Forum Rules: Read This Before Posting


Topic: Identifying inorganic compounds  (Read 6390 times)

0 Members and 1 Guest are viewing this topic.

Offline NYM

  • Regular Member
  • ***
  • Posts: 53
  • Mole Snacks: +2/-0
Identifying inorganic compounds
« on: April 07, 2008, 02:57:38 PM »
Four different solutions in four different test tubes: Na2SO4, K2CO3, Ni(NO3)2 and Na3PO4.

Solution B and solution C each have pH > 7. Solution C and solution D forms a white precipitate with BaCl2. Solution A forms a black precipitate with H2S.
Identify each of the four solutions.


My guesses:
A is Ni(NO3)2: NiS is formed.
B and C are K2CO3 and Na3PO4: pH > 7 (looked at pKB values).
Then D is Na2SO4: BaSO4 is formed.

How do I distinguish B and C? According to my solubility table, both carbonate and phosphate form insoluble salts with Ba2+.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27655
  • Mole Snacks: +1801/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Identifying inorganic compounds
« Reply #1 on: April 07, 2008, 03:31:12 PM »
You are right, and IMHO there is not enough information to answer that question.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline ARGOS++

  • Sr. Member
  • *****
  • Posts: 1489
  • Mole Snacks: +199/-56
  • Gender: Male
Re: Identifying inorganic compounds
« Reply #2 on: April 07, 2008, 04:05:01 PM »
Dear NYM;

Sorry!,  - But IMHO:  After having identified A as Ni(NO3)2 I would use the build HNO3 to release CO2 from K2CO3.
(Or would such not be allowed?)


Good Luck!
                    ARGOS++



Offline NYM

  • Regular Member
  • ***
  • Posts: 53
  • Mole Snacks: +2/-0
Re: Identifying inorganic compounds
« Reply #3 on: April 07, 2008, 04:22:56 PM »
You are right, and IMHO there is not enough information to answer that question.

Good to hear! I'll ask my teacher then.


Dear NYM;

Sorry!,  - But IMHO:  After having identified A as Ni(NO3)2 I would use the build HNO3 to release CO2 from K2CO3.
(Or would such not be allowed?)


Good Luck!
                    ARGOS++

Unfortunately, this is a purely theoretical "lab test." I should be able to solve this without any additional information, but it looks like *somebody* screwed up (could easily be me, though, I just copied this assignment from the black board in the last minute.)


Offline ARGOS++

  • Sr. Member
  • *****
  • Posts: 1489
  • Mole Snacks: +199/-56
  • Gender: Male
Re: Identifying inorganic compounds
« Reply #4 on: April 08, 2008, 04:43:05 PM »

Dear NYM;

Unfortunately! there is absolute no additional or special knowledge required, not at all!

If theoretically or not:
Everybody who uses H2S in this situation your way should/must know:
  • As soon as with H2S any Precipitate is formed from a water-soluble metal-salt, then the corresponding Acid will be build.
  • And there is not many, if any, build Acid that is not easy able to release CO2 from a present “Carbonate”, expect the H2S (pKs ~7.0).
A simple rxn is enough to tell it.

Good Luck!
                    ARGOS++

Offline kevins

  • Chemist
  • Full Member
  • *
  • Posts: 176
  • Mole Snacks: +17/-6
  • I'm a llama!
Re: Identifying inorganic compounds
« Reply #5 on: April 09, 2008, 11:12:20 AM »
Given: Both C and D can form a white ppt with Ba and the pH of C is >7.
So B is K2CO3 because it form a BaCO3 ppt.

Sponsored Links