Al^+3 ions form Al(OH)3 when reacted with NaOH which is a ppt. The ppt dissolves in excess NaOH because of the formation of the complex ion Al(OH)4^-.
Zn ion does the same.
Zn+2 + 2OH^- ==> Zn(OH)2(s)
In excess OH^-, the ppt dissolves because of the formation of the zincate ion.
Zn(OH)2 + 2OH^- ==> Zn(OH)4^-2
The story is a little different for NH3.
For Al^+3, the NH3 forms Al(OH)3(s) but on addition of excess NH3, it does not form a complex ion; therefore, Al(OH)3, although slightly soluble in excess NH3, will not dissolve.
Zn^+2 + NH3 ==> Zn(OH)2(s)
With excess NH3, it dissolves due to the formation of the ammonia complex ion.
Zn(OH)2 + excess NH3 ==> Zn(NH3)4^+ which is soluble.
Al and Zn both form hydroxides when reacted with an NH3 sloution and NaOH solution
The hydroxides are both amphoteric
When you add excess NH3 the Zn ppt dissolves, but Aluminium stays
When you add excess NaOH both ppts dissolve
why doesn't the aluminum ppt dissolve in NH3?
Do the hydroxides form complex ions when reacted with either solution and if they do what are those ions
thank you very much for your help
marysia
2 answers
thanks very much
:)
love marysia
:)
love marysia
2 answers