Write balanced net ionic equations for the reactions that occur in each of the following cases. Identify the spectator ion or ions in each reaction: (a) Cr2(SO4)3(aq) + 3(NH4)2CO3(aq) → 2Cr(CO3)3(s) + 6NH4SO4(aq) Spectator ions: NH4+ and SO4^2- (b) Ba(NO3)2(aq) + K2SO4(aq) → BaSO4(s) + 2KNO3(aq) Spectator ions: K+ and NO3- (c) Fe(NO2)2(aq) + 2KOH(aq) → Fe(OH)2(s) + 2KNO2(aq) Spectator ions: K+ and NO2-
The Correct Answer and Explanation is:
Let’s break down each reaction and find the balanced net ionic equations, along with identifying the spectator ions.
(a) Reaction: Cr2(SO4)3(aq) + 3(NH4)2CO3(aq) → 2Cr(CO3)3(s) + 6NH4SO4(aq)
- Complete Ionic Equation: Cr2(SO4)3(aq)+3NH4CO3(aq)→2Cr(CO3)3(s)+6NH4SO4(aq)\text{Cr}_2(\text{SO}_4)_3(aq) + 3\text{NH}_4\text{CO}_3(aq) \rightarrow 2\text{Cr}(\text{CO}_3)_3(s) + 6\text{NH}_4\text{SO}_4(aq)Cr2(SO4)3(aq)+3NH4CO3(aq)→2Cr(CO3)3(s)+6NH4SO4(aq) This equation involves all species in their ionic forms. Ammonium sulfate (NH4SO4\text{NH}_4\text{SO}_4NH4SO4) and chromium sulfate (Cr2(SO4)3\text{Cr}_2(\text{SO}_4)_3Cr2(SO4)3) dissociate into ions.
- Dissociation into Ions:
- Cr2(SO4)3\text{Cr}_2(\text{SO}_4)_3Cr2(SO4)3 dissociates into 2 Cr3+\text{Cr}^{3+}Cr3+ and 3 SO42−\text{SO}_4^{2-}SO42−.
- NH4CO3\text{NH}_4\text{CO}_3NH4CO3 dissociates into 2 NH4+\text{NH}_4^{+}NH4+ and CO32−\text{CO}_3^{2-}CO32−.
- Net Ionic Equation:
After removing spectator ions (those that appear unchanged on both sides of the equation), we have: 2Cr3+(aq)+3CO32−(aq)→2Cr(CO3)3(s)2\text{Cr}^{3+}(aq) + 3\text{CO}_3^{2-}(aq) \rightarrow 2\text{Cr}(\text{CO}_3)_3(s)2Cr3+(aq)+3CO32−(aq)→2Cr(CO3)3(s)- Spectator ions: NH4+\text{NH}_4^{+}NH4+ and SO42−\text{SO}_4^{2-}SO42−, as these ions do not change during the reaction.
(b) Reaction: Ba(NO3)2(aq) + K2SO4(aq) → BaSO4(s) + 2KNO3(aq)
- Complete Ionic Equation: Ba(NO3)2(aq)+K2SO4(aq)→BaSO4(s)+2KNO3(aq)\text{Ba(NO}_3\text{)}_2(aq) + \text{K}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{KNO}_3(aq)Ba(NO3)2(aq)+K2SO4(aq)→BaSO4(s)+2KNO3(aq) Both barium nitrate and potassium sulfate dissociate into their ions.
- Dissociation into Ions:
- Ba(NO3)2\text{Ba(NO}_3\text{)}_2Ba(NO3)2 dissociates into Ba2+\text{Ba}^{2+}Ba2+ and 2 NO3−\text{NO}_3^{-}NO3−.
- K2SO4\text{K}_2\text{SO}_4K2SO4 dissociates into 2 K+\text{K}^{+}K+ and SO42−\text{SO}_4^{2-}SO42−.
- Net Ionic Equation:
After removing spectator ions: Ba2+(aq)+SO42−(aq)→BaSO4(s)\text{Ba}^{2+}(aq) + \text{SO}_4^{2-}(aq) \rightarrow \text{BaSO}_4(s)Ba2+(aq)+SO42−(aq)→BaSO4(s)- Spectator ions: K+\text{K}^{+}K+ and NO3−\text{NO}_3^{-}NO3−, which do not participate in the formation of the precipitate.
(c) Reaction: Fe(NO2)2(aq) + 2KOH(aq) → Fe(OH)2(s) + 2KNO2(aq)
- Complete Ionic Equation: Fe(NO2)2(aq)+2KOH(aq)→Fe(OH)2(s)+2KNO2(aq)\text{Fe(NO}_2\text{)}_2(aq) + 2\text{KOH}(aq) \rightarrow \text{Fe(OH)}_2(s) + 2\text{KNO}_2(aq)Fe(NO2)2(aq)+2KOH(aq)→Fe(OH)2(s)+2KNO2(aq) Iron(II) nitrite and potassium hydroxide dissociate into ions.
- Dissociation into Ions:
- Fe(NO2)2\text{Fe(NO}_2\text{)}_2Fe(NO2)2 dissociates into Fe2+\text{Fe}^{2+}Fe2+ and 2 NO2−\text{NO}_2^{-}NO2−.
- KOH\text{KOH}KOH dissociates into K+\text{K}^{+}K+ and OH−\text{OH}^{-}OH−.
- Net Ionic Equation:
After removing spectator ions: Fe2+(aq)+2OH−(aq)→Fe(OH)2(s)\text{Fe}^{2+}(aq) + 2\text{OH}^{-}(aq) \rightarrow \text{Fe(OH)}_2(s)Fe2+(aq)+2OH−(aq)→Fe(OH)2(s)- Spectator ions: K+\text{K}^{+}K+ and NO2−\text{NO}_2^{-}NO2−, which remain unchanged during the reaction.
Summary of Spectator Ions:
- (a) NH4+\text{NH}_4^{+}NH4+ and SO42−\text{SO}_4^{2-}SO42−
- (b) K+\text{K}^{+}K+ and NO3−\text{NO}_3^{-}NO3−
- (c) K+\text{K}^{+}K+ and NO2−\text{NO}_2^{-}NO2−
Spectator ions are ions that exist in the same form on both sides of the chemical equation and do not participate in the reaction, remaining unchanged throughout the process.
