Aqueous Solutions

Write what is in the purple boxes

Ionic Equations• When a soluble substance is

dissolved in water, the substance often breaks into ions. This solution is said to be an aqueous solution.

• Pb(NO3)2(aq) Pb2+(aq) + 2NO3-(aq)

• NaI(aq) Na+(aq) + I-(aq)

An aqueous solution is ions dissolved in water

Ionic Equations• Consider the reaction…

• Pb(NO3)2(aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq)

• What is really going on is…• Pb2+ + 2NO3

- + 2Na+ + 2I- PbI2(s) + 2Na+ + 2NO3

-

• Note that the Na+ ion and the NO3- ion are

not reacting. They are said to be spectator ions.

Net Ionic Equations• It is often useful to write an equation

showing only the species that are actually reacting. This is called a net ionic equation. It does not show the spectator ions.Pb2+ + NO3

- + Na+ + 2I- PbI2(s) + Na+ + NO3

-

becomes….

Pb2+(aq) + 2I-(aq) PbI2(s)

Precipitates

• The solid formed from mixing two aqueous solutions is called the precipitate

To predict precipitates, use the Precipitation Diagram

Type of cation

NO3-

Cl- SO4

2- OH- CO32- PO4

3-

Group 1 cations (Na+, K+) and NH4

+

Group 2 cations (Mg2

+, Ca2+,

Ba2+)

BaSO4

Mg(OH)2

Transition metal cations

AgCl

A solid box means a solid forms

Examples

• NaOH(aq) + Cu(NO3)2(aq)

• Na3PO4(aq) + Fe(NO3)3(aq)

• MgSO4(aq) + AgNO3(aq)

• KOH(aq) + NaNO3(aq)