1. Reactions in Aqueous Solutions
Section 10.3

2. Objectives Describe aqueous solutions
Write complete ionic and net ionic equations for chemical reactions in aqueous solutions
Predict whether reactions in aqueous solutions will produce a precipitate, water, or gas.

3. Key Terms Solute Solvent Aqueous solution Complete ionic equation
Spectator ion
Net ionic equation

4. Review of Solutions Solvent- More plentiful substance in solution
Solute- The compound dissolved in the solvent
Aqueous solution- Solution in which the solvent is water

5. Aqueous Solutions Many possible solutes:
Molecular compounds that exist as molecules
Sucrose
Ethanol
Molecular compounds that exist as ions
HCl
HCl(g)  H + (aq) = Cl- (aq)

6. Aqueous Solutions (cont)
Ionic compounds that exist as ions
NaOH
NaOH(aq)  Na + (aq) + OH- (aq)

7. Aqueous Solutions
When two aqueous solutions containing ions react it is always a double replacement reaction.
The water does not react
There are three possible products when aqueous solutions react:
Precipitates
Water
Gases

8. Reactions that form Precipitates
Double-replacement reaction
2NaOH(aq) + CuCl2 (aq)  2NaCl (aq) + Cu(OH)2(s)
Ionic equations are used to show the details of reactions involving ions

9. Writing Ionic Equations
You must show the reactants and the product as ions
A complete ionic equation shows all of the particles in the solution as they realistically exist.
A net ionic equation only shows particles that participate in the reaction.
To write a net ionic equation from a complete ionic equation eliminate all spectators.

10. Complete Ionic Equations
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
What type of reaction is this?
Ag+(aq) + NO3-(aq) + Na+ (aq) + Cl-(aq)  AgCl(s) + Na+ (aq) + NO3-(aq)

11. Spectator Ions
Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq)  AgCl(s) + Na+(aq) + NO3-(aq)
Ions that are not directly involved in a reaction are called spectator ions
They appear on both sides of the arrow exactly the same way

12. Net Ionic Equation Eliminate spectators and rewrite the equation
Ag+(aq) + Cl-(aq)  AgCl(s)

13. Ionic Equations
Make sure that the net charge is balanced. For example…
Pb(s) + 2Cl-(aq)  PbCl2(s)

14. Reactions that Form Water
Double-replacement reactions
Water molecules increase the number of solvent particles
No evidence of reaction is observable (water is colorless and odorless)
HBr(aq) + NaOH(aq)  H2O (l) + NaBr(aq)

15. Practice
Write the complete ionic and net ionic equations for the example:
HBr(aq) + NaOH(aq)  H2O (l) + NaBr(aq)

16. Reactions that Form Gases
Double-replacement reactions
Gas-producing
Common gases:
Carbon dioxide
Hydrogen cyanide
Hydrogen sulfide

17. Practice
Write the complete and net ionic equations for this gas-producing reaction:
2HI(aq) + Li2S(aq)  H2S(g) + 2LiI(aq)

18. Homework
47-51 on page 299