TUTORIAL 11: PRECIPITATION, NEUTRALISATION AND REDOX REACTIONS

1. Classification of Electrolytes

CompoundClassification1.1 HCl (aq)Strong electrolyte1.2 HBr (g)Non-electrolyte (as gas, not dissolved)1.3 CaCO3Non-electrolyte (insoluble in water)1.4 HNO3Strong electrolyte1.5 C12H22O11Non-electrolyte (sucrose, does not ionize)1.6 Ca3(PO4)2Non-electrolyte (insoluble in water)1.7 CH3CH2CH2OHNon-electrolyte (alcohol, does not ionize)1.8 NH3Weak electrolyte1.9 (NH4)2SStrong electrolyte1.10 Al(OH)3Non-electrolyte (insoluble in water)1.11 CCl4Non-electrolyte

2. Solubility in Water

CompoundSolubility2.1 AgIInsoluble2.2 Na2CO3Soluble2.3 BaCl2Soluble2.4 Al(OH)3Insoluble2.5 Zn(CH3COO)2Soluble2.6 (NH4)2CO3Soluble2.7 FeSInsoluble2.8 MgBr2Soluble

3. Dissociation Reactions

• Use single arrow (→) for strong electrolytes/soluble salts, double arrow (⇌) for weak electrolytes/partially soluble.

2.1 AgI (insoluble): No significant dissociation.

2.2 Na2CO3 (soluble): Na2​CO3​(aq)→2Na+(aq)+CO32−​(aq)

2.3 BaCl2 (soluble): BaCl2​(aq)→Ba2+(aq)+2Cl−(aq)

2.4 Al(OH)3 (insoluble): No significant dissociation.

2.5 Zn(CH3COO)2 (soluble): Zn(CH3​COO)2​(aq)→Zn2+(aq)+2CH3​COO−(aq)

2.6 (NH4)2CO3 (soluble): (NH4​)2​CO3​(aq)→2NH4+​(aq)+CO32−​(aq)

2.7 FeS (insoluble): No significant dissociation.

2.8 MgBr2 (soluble): MgBr2​(aq)→Mg2+(aq)+2Br−(aq)

4. Precipitation Reactions

4.1 MgSO4 (aq) + NaCl (aq): No precipitate (all products soluble).

4.2 CaCl2 (aq) + 2 AgNO3 (aq): CaCl2​(aq)+2AgNO3​(aq)→2AgCl(s)+Ca(NO3​)2​(aq) Precipitate: AgCl

4.3 KNO3 (aq) + Sr(OH)2 (aq): No precipitate (all products soluble).

4.4 Ca(OH)2 (aq) + (NH4)3PO4 (aq): 3Ca(OH)2​(aq)+2(NH4​)3​PO4​(aq)→Ca3​(PO4​)2​(s)+6NH4​OH(aq) Precipitate: Ca3(PO4)2

4.5 Ba(NO3)2 (aq) + AgCH3COO (aq): Ba(NO3​)2​(aq)+2AgCH3​COO(aq)→Ba(CH3​COO)2​(aq)+2AgNO3​(aq) No precipitate (all products soluble).

5. Precipitation Reactions: Complete, Net Ionic, Spectator Ions

5.1 Ba(CH3COO)2 (aq) + Na2SO4 (aq)

(a) Ba(CH3​COO)2​(aq)+Na2​SO4​(aq)→BaSO4​(s)+2NaCH3​COO(aq) (b) Net ionic: Ba2+(aq)+SO42−​(aq)→BaSO4​(s) (c) Spectator ions: Na+, CH3​COO−

5.2 NaOH (aq) + CaCO3 (aq)

(a) No reaction (both are soluble/weakly soluble, no precipitate forms). (b) Net ionic: No reaction. (c) Spectator ions: N/A

5.3 Pb(NO3)2 (aq) + KI (aq)

(a) Pb(NO3​)2​(aq)+2KI(aq)→PbI2​(s)+2KNO3​(aq) (b) Net ionic: Pb2+(aq)+2I−(aq)→PbI2​(s) (c) Spectator ions: K+, NO3−​

5.4 Na2S (aq) + Ca(CH3COO)2 (aq)

(a) Na2​S(aq)+Ca(CH3​COO)2​(aq)→CaS(s)+2NaCH3​COO(aq) (b) Net ionic: Ca2+(aq)+S2−(aq)→CaS(s) (c) Spectator ions: Na+, CH3​COO−

6. Cation Identification

A precipitate forms with HBr, H2SO4, and NaOH. Only Ba2+ forms insoluble salts with all three (BaBr2, BaSO4, Ba(OH)2; BaSO4 and Ba(OH)2 are insoluble). So, Ba2+ is the cation present.

7. Acidic or Basic Compounds

CompoundAcidic/Basic7.1 NH4OHBasic7.2 H2S (aq)Acidic7.3 Na2SBasic7.4 Na2CO3Basic7.5 CH3COOHAcidic7.6 HFAcidic7.7 LiHCO3Basic7.8 Ca(OH)2Basic7.9 HClO4Acidic

8. Strong/Weak Acids (Electrolytes)

CompoundStrong/Weak Acid8.1 HIStrong8.2 HClOWeak8.3 H2SWeak8.4 HNO3Strong8.5 H2SO3Weak8.6 HBrStrong8.7 COOHWeak8.8 HClO4Strong

9. Strong/Weak Bases (Electrolytes)

CompoundStrong/Weak Base9.1 KOHStrong9.2 NH4HCO3Weak9.3 Na2SStrong9.4 NH4OHWeak9.5 Li2CO3Weak9.6 HBrNot a base (acid)9.7 CuOHWeak9.8 Ca(OH)2Strong

10. Neutralization Reactions

10.1 HBr (aq) + Ca(OH)2 (aq)

2HBr(aq)+Ca(OH)2​(aq)→CaBr2​(aq)+2H2​O(l)

10.2 H2S (aq) + KOH (aq)

H2​S(aq)+2KOH(aq)→K2​S(aq)+2H2​O(l)

10.3 CH3COOH (aq) + NaHCO3 (s)

CH3​COOH(aq)+NaHCO3​(s)→CH3​COONa(aq)+CO2​(g)+H2​O(l)

10.4 Cu(OH)2 (aq) + HClO4 (aq)

Cu(OH)2​(aq)+2HClO4​(aq)→Cu(ClO4​)2​(aq)+2H2​O(l)

10.5 HCl (aq) + Li2S (aq)

2HCl(aq)+Li2​S(aq)→2LiCl(aq)+H2​S(g)

10.6 H3PO4 (aq) + NH4OH (aq)

H3​PO4​(aq)+3NH4​OH(aq)→(NH4​)3​PO4​(aq)+3H2​O(l)

11. Identification of Unknown Acidic Solution

• The solution is acidic and weakly conducting. Among the options, H3PO3 (phosphorous acid) is a weak acid and weak electrolyte, so it fits the description.

12. Oxidation States

CompoundElementOxidation State12.1 H2SO4S+612.2 HNO3N+512.3 SnCl4Sn+412.4 LiAlH4Al-112.5 Cl2Cl012.6 H2O2O-1

Calculations:

• 12.1 S in H2SO4: 2(+1)+x+4(−2)=0⟹x=+6
• 12.2 N in HNO3: +1+x+3(−2)=0⟹x=+5
• 12.3 Sn in SnCl4: x+4(−1)=0⟹x=+4
• 12.4 Al in LiAlH4: +1+x+4(−1)=0⟹x=−1
• 12.5 Cl in Cl2: x=0 (elemental form)
• 12.6 O in H2O2: 2(+1)+2x=0⟹x=−1