formation of a precipitate

Topic: Reactions in Aqueous Solution

Do Now: Label the following at (aq) or (s)1. NaBr2. PbNO3

3. KOH4. CuSO4

5. Ba2S

Formation of a precipitate

2 aqueous solutions mixing to produce a new compound that is

insoluble (a solid)

Demo

• KI + PbNO3 KNO3 + PbI

• AgNO3 + NaCl AgCl + NaNO3

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 water it splits into the ions that make up

the compound• 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.

Lets check to see if there are really ions

• Conductivity = conduct electricity– Need charged particles (ions) to travel

Electrolytes

• = compounds that conduct electricity• Ionic compounds that dissolve in water are

electrolytes

Dissolving a Covalent Substance in water split into individual molecules NOT IONS

• Ex: sucrose• C12H22O11(s) C12H22O11(aq)• The sugar molecules are spread out among

the water molecules.