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Question
State your observations when ammonium hydroxide solution is added drop by drop and then in excess to each of the following solutions :
1) Copper sulphate solution
2) Zinc sulfate solution.
Solution
When NH4OH is added to copper sulphate solution drop-wise, a pale blue ppt. is obtained.
CuSO4 + 2NH4OH 
Cu(OH)2 + (NH4)2SO4 + 4H2O
With the excess of NH4OH, the ppt. dissolves to give a deep blue solution of tetraamine copper(II)sulphate
Cu(OH)2 + (NH4)2SO4 + 2NH4OH [Cu(NH3)4]SO4 + 4H2O
2) When NH4OH is added to zinc sulphate solution drop-wise, a white, gelatinous ppt. is obtained.
ZnSO4 + 2NH4OH Zn(OH)2 + (NH4)2SO4
With the excess of NH4OH, the ppt. dissolves to give a colorless solution of tetraamine zinc(II)sulphate.
Zn(OH)2 + (NH4)2SO4 + 2NH4OH [Zn(NH3)4]SO4 + 4H2O
RELATED QUESTIONS
What happens when ammonia solution is added first dropwise and then in excess to the following solution:
CuSO4
Write a balanced equation for this reaction.
Name the method used for preparation of the following salt from the list given below:
Zinc ion and Lead ion.
You are provided with PbCO3, ZnCO3 and CaCO3. How will you identify these cations?
Three test tubes contain calcium nitrate solution, zinc nitrate solution and lead nitrate solution.Describe the effect of Adding ammonium hydroxide to each portion in turn till it is in excess.
Write the observation for the following:
NaOH is added drop-wise till in excess to a solution of zinc sulphate.
Write the observation for the following:
Excess NH4OH is added to a substance obtained by adding hydrochloric acid in silver nitrate solution.
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
Write balanced equation copper sulphate solution with ammonium hydroxide solution.
Write balanced equation:
Copper sulphate solution with ammoni um hydroxide solution.
