HW 7 (Sections 16.10-16.13) Problem 16.32 28 of 28 Part A Constants Periodic Tab
ID: 1029490 • Letter: H
Question
HW 7 (Sections 16.10-16.13) Problem 16.32 28 of 28 Part A Constants Periodic Table Explain the observation by writing equilibrium reaction for the first step. Express your answer as a net ionic equation. Identify all of the phases in your answer. In laboratory, a student adds 3 drops of 3 MNHs to a 3 mL of a pale blue solution of 0.1 M Cu(NO3)2 and a precipitate forms. (The presence of Cu ion gives a pale blue solution.) The student then adds 15 more drops of 3 MNHs and the precipitate dissolves and a dark blue solution forms. Refer to Appendix C in the textbook for solubility and complex ion equilibrium reactions and constants Submit Request Answer Part B Explain the observation by writing equilibrium reaction for the second step Express your answer as a net ionic equation. Identify all of the phases in your answer. Submit AnswerExplanation / Answer
For the first part of the reaction, Cu(NO3)2 reacts with NH3 in presence of water to give Cu(OH)2 precipate.
So the overall molecular reaction would be:
Cu(NO3)2 (aq) +2NH3 (aq)+ 2H2O (l) ----------------> Cu(OH)2 (s) + 2NH4NO3 (aq)
The ionic form of the equation would be:
Cu2+ (aq)+ 2NO3-(aq) +2NH4+(aq) + 2OH- (aq) ----------------> Cu(OH)2 (s) + 2NH4+ (aq)+ 2NO3- (aq)
Cancelling the common ions and removing the spectator ions on either sides, will give the net ionic equation:
Cu2+ (aq)+ 2OH- (aq) ----------------> Cu(OH)2 (s)
For the second part of the reaction, adding excess NH3 will push the equilibrium towards formation of a complex of Cu with NH3 with the overall molecular reaction being:
Cu(OH)2 (s) + 4NH3 (aq)----------------> [Cu(NH3)4]2+ (aq) + 2OH- (aq)
The ionic form of the equation would be:
Cu(OH)2 (s) + 4NH3 (aq) ----------------> [Cu(NH3)4]2+ (aq) + 2OH- (aq)
Cu2+ (aq) + 2OH- (aq) +4NH3 (aq) ----------------> [Cu(NH3)4]2+ (aq) + 2OH- (aq)
Cancelling the common ions and removing the spectator ions on either sides, will give the net ionic equation:
Cu2+ (aq) +4NH3 (aq) ----------------> [Cu(NH3)4]2+ (aq)
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