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Reactions in Aqueous Solutions. Chapter 7. Driving Forces of Reactions. Formation of a solid (precipitation reaction) Formation of water (acid-base reaction) Transfer of electrons (oxidation-reduction reaction) Formation of a gas. I. Precipitation reactions.
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Reactions in Aqueous Solutions Chapter 7
Driving Forces of Reactions • Formation of a solid (precipitation reaction) • Formation of water (acid-base reaction) • Transfer of electrons (oxidation-reduction reaction) • Formation of a gas
I. Precipitation reactions • Use solubility rules to determine if a solid is formed (p.170) in the following equations • KNO3 (aq)+BaCl2(aq)KCl (?) + Ba(NO3)2 (?) • Na2SO4(aq)+Pb(NO3)2(aq)NaNO3 (?)+PbSO4(?) • KOH(aq)+Fe(NO3)3KNO3(?)+Fe(OH)3(?)
Answers • KNO3 (aq)+BaCl2(aq)KCl(aq) + Ba(NO3)2 (aq) This reaction will not occur because a solid is not formed • Na2SO4(aq)+Pb(NO3)2(aq)NaNO3 (aq)+PbSO4(s) This chemical reaction will occur • KOH(aq)+Fe(NO3)3KNO3(aq)+Fe(OH)3(s) This chemical reaction will occur
II Formation of Water • In an acid base reaction, salt (ionic compounds) and water always form. • HCl(aq) + NaOH (aq)HOH (l) + NaCl (aq) acid base water salt • This is the molecular equation-represents the complete formulas of the reactants and products • However, we can also write an ionic equation-where the electrolytes are represented as ions (solids and liquids are not broken up) • H+(aq) +Cl-(aq)+Na+(aq) +OH-(aq)H2O(l) +Na+(aq) +Cl-(aq) • We can also write a net ionic equation-take out the spectator ions (those not involved making a solid or liquid) • H+(aq)+OH-(aq)H2O(l) *Na+ and Cl- are present on both sides so we take them out of the net ionic equation
Practice • Write the molecular, ionic, and net ionic equations for the following reaction • Aqueous potassium chromate reacts with aqueous barium nitrate
Answers • Molecular K2CrO4 (aq) + Ba(NO3)2BaCrO4 (s) + 2KNO3(aq) • Ionic 2K+1(aq)+CrO4-2(aq) + Ba+2(aq)+2NO3-1(aq)BaCrO4 (s) + 2K+(aq)+2NO3-1(aq) • Net Ionic CrO4-2 (aq) + Ba+2(aq)BaCrO4 (s)
III Transfer of electrons • Oxidation-loss of electrons • Reduction-gain of electrons • Oxidation/reduction reaction-metal/nonmetal reaction (sometimes nonmetals undergo ox/red if oxygen is a reactant) • 2Na(s)+Cl2(g)2NaCl(s) • Na + Cl Na++ Cl- oxidation reduction
IV Formation of a gas • 2AlN (s) 2Al (s) + N2 (g)