1) Describe an experiment to distinguish between Al3+ and Zn2+.
2) Some students tried to prepare dry ammonia gas in the lab using the following apparatus: Bunsen burner, boiling tube, U-tube, gas jar, delivery tubes with stoppers*3, rubber tubing.
a) suggest suitable solid reactant and a drying agent for this experiment.
b) Write a chemical equation for the above information of ammonia.
(P.S. for Q1, both ions form complexes and redissolve in acid, no way to distinguish?
for Q2, how to prepare NH3 in the lab?
Thanks so much.)
F.4 chem questions x2
2009-06-06 7:16 pm
回答 (2)
2009-06-07 7:14 am
✔ 最佳答案
1.Add separately ammonia solution dropwise until excess to each solution.
Solution containing Al3+:
A white gelatinous precipitate of aluminium hydroxide is formed, and the precipitate does not re-dissolve in excess ammonia solution.
NH3(aq) + H2O(l) ≒ NH4+(aq) + OH-(aq)
Al3+(aq) + 3OH-(aq) → Al(OH)3(s)
Solution containing Zn2+:
A white precipitate of zinc hydroxide is formed, and the precipitate re-dissolves in excess ammonia solution to form a colourless solution.
NH3(aq) + H2O(l) ≒ NH4+(aq) + OH-(aq)
Zn2+(aq) + 2OH-(aq) → Zn(OH)2(s)
Zn(OH)2(s) + 2OH-(aq) → [Zn(OH)4]2-(aq)
2.
(a)
Solid reactants: ammonium chloride and sodium hydroxide (or calcium hydroxide)
(an ammonia salt and a solid strong base)
Drying agent: calcium oxide (or soda lime)
(b)
NH4Cl(s) + NaOH(s) → NaCl(s) + H2O(g) + NH3(g)
(2NH4Cl(s) + 2Ca(OH)2(s) → CaCl2(s) + 2H2O(g) + 2NH3(g))
=
2009-06-06 7:45 pm
1Add them into ammonia solution respectively
observation:Zn2+ form a white precipitate which redissolves in
excess ammonia solution while the white precipitateformed by Al3+ does not .
2009-06-06 11:51:19 補充：
2.a) solid reactant :sodium sulphite
drying agent : calcium oxide
b) SO^2-+2H^+ --> SO2+ H20
2009-06-06 11:56:55 補充：
The method for preparingNH3 in the lab is :
React Sodium sulphite whith an acid
chemical equation : SO^2-+2H^+ --> SO2+ H20
2009-06-06 18:21:33 補充：
希望我可以幫到您啦=)
仲有冇野唔明,如果有的,就問啦!我係好樂意解答啦=)
observation:Zn2+ form a white precipitate which redissolves in
excess ammonia solution while the white precipitateformed by Al3+ does not .
2009-06-06 11:51:19 補充：
2.a) solid reactant :sodium sulphite
drying agent : calcium oxide
b) SO^2-+2H^+ --> SO2+ H20
2009-06-06 11:56:55 補充：
The method for preparingNH3 in the lab is :
React Sodium sulphite whith an acid
chemical equation : SO^2-+2H^+ --> SO2+ H20
2009-06-06 18:21:33 補充：
希望我可以幫到您啦=)
仲有冇野唔明,如果有的,就問啦!我係好樂意解答啦=)
參考: , ME, ME
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