Understanding Reactions in Aqueous Solutions: Dissolving, Precipitation, and Gas Formation
This overview explores the dynamics of reactions in aqueous solutions, particularly focusing on double replacement reactions. It discusses how ionic and covalent substances dissolve differently in water, illustrated by examples such as sugar and table salt. Additionally, the text addresses the formation of solids through precipitation and reactions producing gases, presenting relevant chemical equations. The importance of conservation of charge in these reactions is also highlighted, ensuring that the total charge on reactants equals that on products.
Understanding Reactions in Aqueous Solutions: Dissolving, Precipitation, and Gas Formation
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Presentation Transcript
Reactions in aqueous solution • Many reactions, esp. many double replacement reactions, occur in water. • What happens when substances dissolve in water? • Depends on if they are ionic or covalent.
Dissolving • Covalent substance – sugar or C6H12O6 • C6H12O6(s) C6H12O6(aq) • The sugar molecules are spread out among the water molecules.
Dissolving • Ionic substance – table salt or NaCl • NaCl(s) Na+(aq) + Cl-(aq) • CaCl2(s) Ca2+(aq) + 2Cl-(aq) • AlCl3(s) Al3+(aq) + 3Cl-(aq) • The ions are spread out among the water molecules.
Double Replacement Reactions • Often occur when you mix 2 solutions of ionic compounds. • 1 product may be water or • 1 product may be a gas or • 1 product may be a solid • We say these reactions “go to completion.”
Reactions producing Solids • Precipitation: the opposite of dissolving! • What do you see in the following clips: • S1043.mov • S1045.mov • S1046.mov • S1050.mov • S1057.mov • S1058.mov and S1060.mov
Reactions producing Solids 2 NaOH(aq) + CuCl2(aq) 2 NaCl(aq) + Cu(OH)2(s) Complete Chemical Equation
Complete Ionic Equations 2Na+(aq) + 2OH-(aq) + Cu2+(aq) + 2Cl-(aq) 2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s) Ionic substances that dissolve are written as ions in solution!
Net Ionic Equations 2Na+(aq) + 2OH-(aq) + Cu2+(aq) + 2Cl-(aq) 2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s) Notice that some ions do not participate in the reaction. They are spectator ions. Cross out all the spectator ions & you get the net ionic equation. 2OH-(aq) + Cu2+(aq) Cu(OH)2(s)
Reactions that form Water HBr(aq) + NaOH(aq) H2O(l) + NaBr(aq) H+(aq) + Br-(aq) + Na+(aq) + OH-(aq) H2O(l) + Na+(aq) + Br-(aq) H+(aq) + OH-(aq) H2O(l)
Reactions that form Gases HCl(aq) + NaHCO3(aq) H2CO3(aq) + NaCl(aq) H2CO3(aq) H2O(l) + CO2(g) ______________________________________ HCl(aq) + NaHCO3(aq) H2O(l) + CO2(g) + NaCl(aq)
Reactions that form Gases HCl(aq) + NaHCO3(aq) H2O(l) + CO2(g) + NaCl(aq) H+(aq) + Cl-(aq) + Na+(aq) + HCO3-(aq) H2O(l) + CO2(g) + Na+(aq) + Cl-(aq) H+(aq) + HCO3-(aq) H2O(l) + CO2(g)
Conservation of Charge • Total charge on reactant side must equal total charge on product side.
