CHEMISTRY 161 Chapter 4

CHEMICAL REACTIONS 2 HgO (s) → 2Hg (l) + O 2(g) aq 1. properties of solutions 2. reactions in solutions a) precipitation reactions b) acid-base reactions (proton transfer) c)redox reactions (electron transfer)

1. SOLUTION homogeneous mixture of two or more substances solvent solute substance in a large amount substance in a small amount N 2 gas phase O 2 (air) Ag solid phase Au (alloys) H 2 O liquid phase NaCl (sea water)

1.1. GAS PHASE SOLUTION Saturn solvent H 2 /He solute CH 4, PH 3

1.2. SOLID SOLUTION Triton solvent N 2 solute CH 4

1.3. LIQUID SOLUTION Titan solvent C 2 H 6 solute CH 4

1.3. LIQUID SOLUTION Europa solvent H 2 O solute Mg 2 SO 4

AQUEOUS SOLUTION solutes solute water (H 2 O) electrolytesnon-electrolytes solution conducts electricity solution does not conduct electricity

electrolytesnon-electrolytes solution conducts electricity solution does not conduct electricity

non-electrolyte weak electrolyte strong electrolyte methanol sugar ethanol water darkbright ionic compounds NaOH HCl H 2 SO 4 CH 3 COOH HCOOH HF medium

electric current I [A] = Q [C]/ t[s] migrating negative and positive charges Kohlrausch NaCl

measuring the electric current - + anodecathode anodecathode NaCl

DISSOCIATION ‘breaking apart’ NaCl (s) → Na + (aq) + Cl - (aq) NaOH (s) → Na + (aq) + OH - (aq) HCl (g) → H + (aq) + Cl - (aq) strong electrolytes are fully dissociated

CH 3 COOH (aq) H + (aq) + CH 3 COO - (aq) weak electrolytes are not fully dissociated reversible reaction (chemical equilibrium) → ← O HH δ-δ- δ+δ+ δ+δ+

SOLVATION cationsanions

2.1. PRECIPITATION REACTIONS formation of an insoluble product (precipitate) NaCl(aq) + AgNO 3 (aq) AgCl(s) + NaNO 3 (aq)

insoluble compounds 1.M + compounds (M = H, Li, Na, K, Rb, Cs, NH 4 ) 2. A - compounds (A = NO 3, HCO 3, ClO 3, Cl, Br, I) (AgX, PbX 2 ) 3. SO 4 2- (Ag, Ca, Sr, Ba, Hg, Pb) 4. CO 3 2-, PO 4 3-, CrO 4 2-, S 2- (exception: M + )

NaCl(aq) + AgNO 3 (aq) → AgCl(s) + NaNO 3 (aq) balanced molecular equation

balanced ionic equation 1. NaCl(s) → Na + (aq) + Cl - (aq) 2. AgNO 3 (s) → Ag + (aq) + NO 3 - (aq) 3. Na + (aq) + Cl - (aq) + Ag + (aq)+ NO 3 - (aq) → AgCl(s) + Na + (aq) + NO 3 - (aq) spectator ions

Ba(NO 3 ) 2 + Na 2 SO 4 → BaSO 4 + NaNO 3 1.balanced molecular equation 2. balanced ionic equation 3. spectator

SUMMARY 1.solution, solvent, and solute 2. experimental definition of strong/weak/non-electrolyte 3. dissociation and hydration of solute in solvent (solutions conduct electricity) 4. precipitation reaction (molecular equation, ionic equation, spectator ions)

Homework Chapter 4, p problems