Topic: Reactions in Aqueous Solution

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Formation of a precipitate

2 aqueous solutions mixing to produce a solid

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 an Ionic Substance in a WaterIonc Dissolution (IONS)

• Example: • 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.

Dissolving a Covalent Substance in waterMolecular Dissolution (molecules)

• Ex: glucose• C6H12O6(s) C6H12O6(aq)• The sugar molecules are spread out among

the water molecules.

Not everything dissolves in water

• Soluble = dissolves in water• Insoluble = doesn’t dissolve in water• Miscible = 2 liquids that dissolve• Immiscible = 2 liquids that don’t dissolve

How can you tell….?!!!??• Like Dissolve Like– Water is polar, so most polar compounds will dissolve in

water• All ionic compounds are polar– Use table F to see if it will dissolve in water

• Covalent compound– Polar will dissolve in water– Nonpolar will not dissolve in water

• NP (LOOK AT MOLECULAR SHAPE!)– Diatomic– Nobel gas– Pure hydrocarbon– Small symmetrical

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:-TIGER VIDEOS

Reactions producing Solids

p. 1 in your packet

Complete Ionic Equations

2K+1(aq) + CrO4

-2(aq) + Ba2+

(aq) + 2NO3-1

(aq) 2K+(aq)+ 2NO3

-1(aq)+ BaCrO4(s)

Ionic substances that dissolve are written as ions in solution!

Net Ionic Equations2K+1

(aq) + CrO4-2

(aq) + Ba2+(aq) + 2NO3

-1(aq) 2K+

(aq)+ 2NO3-1

(aq)+ BaCrO4(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.

CrO4+2

(aq)+ Ba2+(aq) BaCrO4(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) 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.

• Mass of reactants = mass of products• Total # Atoms of reactants = Total # Atoms of products

Conservation of Mass