Question

# Write the equations that correspond to the chemical changes that occured on treating each of the...

Write the equations that correspond to the chemical changes that occured on treating each of the carbonate/hydroxide precipitates [1) Fe (III), [2) Cu(II), [3) Zn(II), and 4) Ag (I] with

A) 6M NH3 (if no reaction occurs, write NR)

B) 6M NaOH (If no reaction occurs, write NR)

A) 6M NH3

This reaction occurs because ammonia is a weak base:
NH3(aq) + H2O(l) <--> NH4+(aq) + OH-(aq)
Three OH- then react with the Fe3+ to give a precipitate of Fe(OH)3. So overall, the equation is:
Fe3+(aq) + 3NH3(aq) + 3H2O --> Fe(OH)3(s) + 3NH4+(aq)

Dilute ammonia: you get precipitation:

Cu2+ + 2 NH3 + 2 H2O --> Cu(OH)2 + 2 NH4+

Excess ammonia: complex formation (lovely deep blue):

Cu2+ + 4 NH3 --> Cu(NH3)4 2+

Zn2+ + 4 NH3 --> [Zn(NH3)4](2+)

Ag+(aq) + 2 NH3(aq) ↔ Ag(NH3)2+(aq)

B) 6M NaOH

CuCO3 (aq) + NaOH (aq) -> Cu(OH)2 (s) +Na2CO3 (s)

ZnCO3 + NaOH = Na2[Zn(OH)4] + Na2CO3

AgCO3 + NaOH ----> Na2CO3 + AgOH