Reactions in Aqueous Solutions Chemistry B2A Chapter 7 Reactions in Aqueous Solutions

Aqueous solution: solvent is water Reactions in Aqueous Solutions Ionic compounds Aqueous solution: solvent is water

Reactions in Aqueous Solutions Chemical reactions that occur in water. In our body reactions occur in the aqueous solution.

Water in our body About 60% of our body. Most of the reactions occur in aqueous solution. Participates in many biochemical reactions. Transports reactants and products from one place in our body to another. 5. Eliminates the waste materials from cells and our body (urine).

Why does a chemical reaction occur? Several driving forces: Formation of a solid Formation of water Transfer of electrons Formation of a gas

Why does a chemical reaction occur? Several driving forces: Formation of a solid Formation of water Transfer of electrons Formation of a gas

Precipitation reactions Formation of a solid Precipitation reactions Precipitate KI + Pb(NO3)2  ?

Ionic Compounds When an ionic compound dissolves in water, ions are produced. Ions Hydrated by H2O Hydration

Ionic Compounds Soluble solid: it completely dissolves in water (ions are formed). Slightly soluble solid: it partially dissolves in water. Insoluble solid: it does not dissociate in water (almost). Ionic compounds = Salts

All nitrates (NO3-) and acetate (CH3COO-) are soluble in water. Ionic Compounds All nitrates (NO3-) and acetate (CH3COO-) are soluble in water. Most salts of Na+, K+, and NH4+ are soluble in water. Most chlorides (Cl-) and sulfates (SO42-) are soluble in water. (except AgCl, PbCl2, BaSO4, CaSO4, PbSO4) Most carbonates (CO32-), phosphates (PO43-), Sulfide (S2-), and hydroxides (OH-) are insoluble in water. (except NaOH, KOH, Ba(OH)2, Ca(OH)2, and NH4OH)

Electrolytes + - Electrolyte: conducts an electric current. Na+ Cl- bulb Electrolyte: conducts an electric current. Ionization (Dissociation) NaCl → Na+ + Cl- strong electrolytes: molecules dissociate completely into ions (NaCl). weak electrolytes: molecules dissociate partially into ions (CH3COOH). nonelectrolytes: molecules do not dissociate into ions (DI water).

Precipitation reactions Formation of a solid Precipitation reactions Precipitate KI + Pb(NO3)2  ?

Aqueous Solution (ionic compounds) aqueous solution: solvent is water H2O Dissociation (Ionization) KI(s) K+(aq) + I-(aq) KI K+ I- H2O Pb(NO3)2 Pb(NO3)2(s) Pb2+(aq) + 2NO3-(aq) Pb2+ NO3- NO3-

Aqueous Solution (ionic compounds) KI Pb(NO3)2 K+ I- Pb2+ NO3- 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq)

total charge on left side = total charge on right side Molecular equation: 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq) Complete Ionic equation: 2K+(aq) + Pb2+(aq) + 2I-(aq) + 2NO3-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq) 2K+(aq) + Pb2+(aq) + 2I-(aq) + 2NO3-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq) Pb2+(aq) + 2I-(aq)  PbI2(s) Net ionic equation: Spectator ions 2As3+(aq) + 3s2-(aq)  As2S3(s) total charge on left side = total charge on right side balanced equation

Why does a chemical reaction occur? Several driving forces: Formation of a solid Formation of water Transfer of electrons Formation of a gas

Acids and Bases Acids: sour Bases: bitter or salty

Acids and Bases Arrhenius definition: Acid: produces H3O+ (H+) in water. CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq) H3O+ (Hydronium ion): H+(aq) + H2O(l) H3O+(aq) Base: produces OH- in water. H2O NaOH(s) Na+(aq) + OH-(aq) NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

Weak acid and base: it is partially ionized in aqueous solution. Acids and Bases Weak acid and base: it is partially ionized in aqueous solution. produces less H+ and OH- CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq) NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) Strong acid and base: it is completely ionized in aqueous solution. produces more H+ and OH- HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq) NaOH(aq) + H2O(l) Na+(aq) + OH-(aq)

Acid-Base Reactions Neutralization A strong acid and a strong base react together to produce a salt and water. NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) +  Na+(aq) + Cl-(aq) + H2O(l) H+(aq) + OH-(aq) H2O(l) The only chemical change is the formation of water.

Why does a chemical reaction occur? Several driving forces: Formation of a solid Formation of water Transfer of electrons Formation of a gas

Metal + Nonmetal : Transfer of electrons Oxidation and Reduction reactions (redox) e- 2Na(s) + Cl2(g) 2NaCl(s) Na → Na+ + e- Cl + e- → Cl- Metal + Nonmetal : Transfer of electrons Oxidation and Reduction reactions (redox)

oxidation: it is the loss of electrons. Oxidation and Reduction reactions (redox) oxidation: it is the loss of electrons. reduction: it is the gain of electrons. Zn(s) + Cu2+(aq)  Zn2+(aq) + Cu(s) redox reaction Zn(s)  Zn2+(aq) + 2e- Zn is oxidized (reducing agent) Cu2+(aq) + 2e-  Cu(s) Cu2+ is reduced (oxidizing agent)

oxidation: is the gain of oxygen / loss of hydrogen. Oxidation and Reduction reactions (redox) oxidation: is the gain of oxygen / loss of hydrogen. reduction: is the loss of oxygen / gain of hydrogen. CH4(s) + 2O2(g)  CO2(g) + 2H2O(g) redox reaction C gains O and loses H is oxidized (reducing agent) O gains H Is reduced (oxidizing agent) single replacement reaction and combustion reactions  redox reactions double replacement reactions  non redox

Classification of chemical reactions Precipitation Reactions Oxidation-Reduction Acid-Base Combustions Synthesis (combination) (Reactants are elements.) Decomposition (Analysis) (Products are elements.)