A cation qualitative analysis in lab incuding the cations Al, Zn, Mn(II), Ni(II)

Question

A cation qualitative analysis in lab incuding the cations Al, Zn, Mn(II), Ni(II) and Iron(III) was performed. Complete and balance the following as net ionic equations. If the reaction takes place in two steps (precipitation, complexation with excess reagent), give each equation.

The first one has been completed for you as an example with ammonium hydroxide.

Reactions with ammonium hydroxide:

Al3+(aq) + 3NH3(aq) + 3H2O(l) --> Al(OH)3(s) + 3NH4+(aq)

or Al3+(aq) + 3NH4OH(aq) --> Al(OH)3(s) + 3NH4+(aq)

Reactions with sodium hydroxide:

Al3+(aq) +

Fe3+(aq) +

Mn2+(aq) +

Ni2+(aq) +

Zn2+(aq)+

Explanation / Answer

a) The balanced ionic equation is :

Al3+(aq) + 3NaOH(aq) Al(OH)3(s) +3 Na+ (aq)

This compound is amphoteric which means it can act as both an acid and a base.

So if excess hydroxide ions are added

Al(OH)3(s) + NaOH(aq)Na[Al(OH)4](aq)

b) Fe3+ (aq)+ 3NaOH(aq) ® Fe(OH)3 (s) +3 Na+ (aq)

c) Mn2+(aq) + 2NaOH(aq) ®Mn(OH)2(s) + 2 Na+ (aq)

d) Ni2+(aq) + 2NaOH(aq) ® Ni(OH)2(s) + 2 Na+ (aq)

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