I need help with net ionic equations . My answers seem off. I would appreciate s

Question

I need help with net ionic equations. My answers seem off. I would appreciate someone double-checking and providing feedback. Thank you in advance.

1a) To the following precipitates, add HNO3 and write out the NIE: Pb(OH)2(s), Al(OH)3 (s), Fe(OH)3 (s), Cr(OH)3 (s)

My answers: Pb(OH)2 (s) + 2H (aq) --> Pb (aq) + 2H2O (l)
Al(OH)3 (s) + 3 H+ (aq) --> Al (aq) + 3 H2O (l)
Fe(OH)3 (s) + 3 H+ (aq) --> Fe (aq) + 3H2O (l)
Cr(OH)3 (s) + 3 H+ (aq) ---> Cr + 3H2O (l)

1b) Then add (NH4)2SO4 to the soultion from step 1a. Write out NIE.

My answers:
Pb (aq) + SO4 (aq) --> Pb(SO4) (s)
No rxn for other ones? All ions were spectators but this doesn't seem right because the third question asks...

1c) Get rid of precipitate rxn. Then add NH3 to the rest of solutions and write out NIE.

THANK YOU!

Explanation / Answer

1a)On adding HNO3 to the mixture of precipitates Pb(OH)2(s), Al(OH)3 (s), Fe(OH)3 (s), Cr(OH)3 (s) due to acidic medium all of them get dissolved and the net ionic reactions for them are:

Pb (OH)2(s) + 2H+(aq.) --------> Pb2+(aq.) + 2H2O (l)

Al (OH)3(s) + 3H+(aq.) --------> Al3+ (aq.) + 3 H2O (l)

Fe (OH)3(s) + 3H+(aq.) --------> Fe3+ (aq) + 3H2O (l)

Cr (OH)3(s) + 3H+ (aq.) -------> Cr3+(aq.) + 3H2O (l)

Note :In all above NO3- (nitrate) ions are also present but cancelled out from both sides and hence do not appear in net ionic reaction.

================================================================================

1b)Then to the solution containing all these cations on adding (NH4)2SO4 only Pb2+ get precipitate out as the salt Pb(SO4)2 is only insoluble in water.

Net ionic reaction for this is:

Pb2+(aq.) + SO42- (aq.) ------------> Pb(SO4)2 (s)

==================================================================================

1c) Lead sulphate [Pb (SO4)2] precipitate formed in 1b step is then filtered off and separated. The filtrate then added with aq.NH3 solution (i.e. NH4OH) which resets the basic condition and precipitate out remaining cations back. The net ionic reactions for their precipitation are:

Al3+(aq.) + 3HO-(aq.) --------> Al(OH)3(s)

Fe3+(aq.) + 3 HO-(aq.) --------> Fe(OH)3(s)

Cr3+(aq.) + 3 HO- (aq.) -------> Cr(OH)3(s)

====================================================================================

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.