1. Reactions in Aqueous Solutions
Ms. Mack
Chapter 10, Section 3
Chemistry I- 3/24/09

2. Water is the "universal solvent"
Introduction
Many reactions involve substances dissolved in water.
When this happens, solutions form
Solutions (homogeneous substances)
Two parts:
SOLUTES- substances dissolved in water
SOLVENTS- the most plentiful substance in a solution
Water is the "universal solvent"

3. Water, the universal solvent (H2O)
Examples of Solutes:
Molecular compounds that exist as molecules
Molecular compounds that form ions when they dissolve in water (H+ ions=acids)
Ionic compounds
When dissolved in water, the ions can separate

4. The Products
When 2 aqueous solutions that contain ions are combined, the ions may react with one another in a DOUBLE-REPLACEMENT reaction producing:
A. Precipitate (s)
B. Water (l)
C. Gas (g)

5. A. Precipitate
Use ionic equations to show the details of reactions that involve ions in aqueous solutions
Substances are written as ions
Complete ionic equations- show all particles involved in a chemical reaction

6. Complete Ionic Equation
NaCl (aq) + AgNO3 (aq) NaNO3 (aq) + AgCl (s)
Complete:
Na+(aq) + Cl- (aq) + Ag+ (aq) + NO3-(aq) Na+ (aq) + NO3- (aq) + AgCl (s)

7. Spectator Ions
Notice, that there are ions that appear on both sides of the equation
These ions do not participate in the formation of the solid product
These ions are called spectator ions.
What were the spectator ions in the previous slide?

8. Net Ionic Equations
Equations that show only the ions involved- omitting the spectator ions are called complete ionic equations!
From the previous example:
Cl- + Ag+ AgCl (s)

9. Practice!
Write the chemical, balanced, complete ionic and net ionic equation for the following:
Aqueous solutions of potassium iodide and silver nitrate are mixed, forming the precipitate silver iodide.
See white board for solution!

10. B. Water Some reactions form water
No evidence of the chemical reaction can be observed. Why?
Example:
HCl (aq) + KOH (aq) H2O (l) + KCl (aq)
H+ (aq) + OH- (aq) H2O (l)

11. Practice!
Sulfuric acid (H2SO4) and aqueous potassium hydroxide react to produce water and potassium sulfate.

12. C. Gas
Common gases produced: carbon dioxide, hydrogen cyanide, and hydrogen sulfide
Example:
Na2S (aq) + HCl (aq) NaCl (aq) + H2S (g)

13. Practice!
Sulfuric acid and aqueous rubidium sulfide with production of hydrogen sulfide gas