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Chapter 5 Chemical Reactions
Dissolution of (a) Ionic and (b) Molecular Compounds
Electrolytes All salts are strong electrolytes, that is they dissociate into ions in solution If they are significantly soluble then the dissolved ions make the solution a good conductor of electricity Molecular compounds except for acids and bases are non-electrolytes, non-conductors
Exceptions in red may show up on exams
Illustration of Some Solubility Rules
Which of the following salts is insoluble in water Na2S (NH4)3PO4 Ag2SO4 Ba(OH)2 AgI 130 10
Precipitation Reactions If either of the possible products of a double replacement are in soluble then a precipitate will form. A chemical reaction occurs. If both possible products are soluble there is no reaction.
Precipitation of Silver Chloride AgNO3 + NaCl AgCl + NaNO3 precipitate
Mixing which of the following pairs of solutions will result in formation of a precipitate? NaCl and Ba(NO3)2 K2SO4 and Ba(C2H3O2)2 FeSO4 and KI NaBr and Cr(NO3)3 MgSO4 and CuCl2 130 10
Writing equations for Precipitation Reactions Na3PO4 + FeSO4 Swap partners – Na2SO4 + Fe3(PO4)2 Check solubility rules – Fe3(PO4)2 is insoluble Write unbalanced equation – Na3PO4(aq)+FeSO4(aq)Na2SO4(aq)+Fe3(PO4)2(s) Balance – 2Na3PO4(aq)+3FeSO4(aq)3Na2SO4(aq)+Fe3(PO4)2(s)
Ionic Equations Write the balanced equation of reaction 2Na3PO4(aq)+3FeSO4(aq)3Na2SO4(aq)+Fe3(PO4)2(s) Total Ionic Equation – Separate all aqueous strong electrolytes into ions: 6Na+(aq) + 2PO43-(aq) + 3Fe2+(aq) + 3SO42-(aq) 6Na+(aq) + 3SO42-(aq) + Fe3(PO4)2(s) Net Ionic Equation – Eliminate spectator ions 2PO43-(aq) + 3Fe2+(aq) Fe3(PO4)2(s)
Acids substances that donates H+ ions to solution sour-tasting substances substances whose aqueous solutions are capable of turning blue litmus indicators red dissolves certain metals to form salts react with bases or alkalis to form salts
Bases substances that donates a OH- ion to solution hydroxides and oxides of metals bitter tasting, slippery solutions turn litmus blue react with acids to form salts
Ionization of Acids in Water Strong electrolyte Weak electrolyte
Common Acids and Bases Learn All others are weak
Neutralization Reactions acid + base “salt” + water HCl + NaOH NaCl + H2O H2SO4 + 2KOH K2SO4 + 2H2O
Strong vs. Weak Acids and Bases strong – completely ionized separate into ions in ionic equation weak – partially ionized keep intact in ionic equation
Ionic Equations HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) Total Ionic Equation: H+ + Cl- + Na+ + OH- Na+ +Cl- + H2O Net Ionic Equation: H+(aq) + OH-(aq) H2O(l)
Ionic Equations H3PO4(aq) + 3KOH(aq) K3PO4(aq) + 3H2O(l) Total Ionic Equation: H3PO4 + 3K+ + 3OH- 3K+ + PO43- + 3H2O Net Ionic Equation: H3PO4(aq) + 3OH-(aq) PO43-(aq) + 3H2O(l)
What is the net ionic equation for the reaction of acetic acid with NaOH? H++OH-H2O H++NaOHH2O+Na+ CH3COOH+OH-CH3COO-+H2O Na++ CH3COO-NaCH3COO 130 10
Gas-Forming Exchange Reaction
Reaction of Metal Carbonates with Acids CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2CO3(aq) H2CO3(aq) H2O + CO2(g) Carbonic acid is unstable and releases carbon dioxide gas Total Ionic Equation: CaCO3(s) + 2H+ + 2Cl- Ca2+ + 2Cl- + H2O + CO2(g) Net Ionic Equation: CaCO3(s) + 2H+(aq) Ca2+(aq) + H2O(l) + CO2(g)
Reaction of Metal Sulfites and Sulfides with Acids CaSO3(s) + 2HCl(aq) CaCl2(aq) + H2SO3(aq) H2SO3(aq) H2O + SO2(g) Net Ionic Equation: CaSO3(s) + 2H+(aq) Ca2+(aq) + H2O(l) + SO2(g) Na2S(aq) + 2HCl(aq) 2NaCl(aq) + H2S(g) S2-(aq) + 2H+(aq) H2S(g)
Which of the following is a gas forming reaction? Na2CO3+Ba(OH)2 AgNO3+Na2S ZnCO3+HNO3 HCl+CuSO4 130 10