Advertisements
Advertisements
प्रश्न
You are provided with PbCO3, ZnCO3 and CaCO3. How will you identify these cations?
Advertisements
उत्तर
By use of Ammonium hydroxide we can identify the ions PbCO3, ZnCO3 and CaCO3 as :
(i) \[\ce{PbCO3 + 2NH4OH -> Pb(OH)2 v + 2NH4NO3}\]
Pb(OH)2 forms white precipitate which are insoluble in excess ammonium hydroxide.
(ii) \[\ce{ZnCO3 + NH4OH -> Zn(OH)2 v + 2Na2CO3}\]
Zn(OH)2 forms white gelatinous precipitate which are soluble in excess ammonium hydroxide.
(iii) \[\ce{CaCO3 + NH4OH -> Ca(OH)2 + 2Na2CO3}\]
No precipitation of Ca(OH)2 occurs even with addition of excess of NH4OH. Because the concentration of hydroxide ion from ammonium hydroxide is so low that it cannot precipitate the hydroxide of calcium.
Concept Insight : Some precipitated metallic hydroxides by ammonium hydroxide become soluble hydroxides when treated with excess of ammonium hydroxide due to the formation of a soluble complex salt in the presence of excess of ammonium hydroxide.
APPEARS IN
संबंधित प्रश्न
How will you distinguish between Ammonium hydroxide and Sodium hydroxide using copper sulphate solution?
What happens when ammonia solution is added first dropwise and then in excess to the following solution:
FeCl3
Write a balanced equation for this reaction.
Name the metal hydroxides which are soluble in ammonium hydroxide solution.
State two relevant observations of the following:
Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantities and then in excess.
Write the observation for the following :
NH4OH is added first in a small quantity and then in excess to a solution of copper sulphate.
The following table shows the tests a student performed on four different aqueous solutions which are X,Y,Z and W. Based on the observations provided, Identify the cation present
|
Chemical Test |
Observation | Conclusion |
| To Solution X, ammonium hydroxide is added in minium quantity first and then in excess | A dirty white precipitate is formed which dissolves in excess to form a clear solution | (i) |
| To Solution Y, ammonium hydroxide is added in minimum quantity first and then in excess | A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution | (ii) |
| To solution W, A small quantity of sodium hydroxide solution is added and then in excess | A white precipitate is formed which remains insoluble | (iii) |
| To a salt Z, calcium hydroxide solution is added and then heated | A pungent smelling gas turning moist red litmus paper blue is obtained | (iv) |
Identify the cation of the following case:
NaOH solution when added to solution (A) gives a reddish brown precipitate
Identify the cation of the following case:
NH4OH solution when added to solution (B) gives white ppt. which does not dissolve in excess.
Write balanced equation:
Copper sulphate solution with ammoni um hydroxide solution.
Write balanced equation:
Copper sulphate solution with ammonium hydroxide solution.
