1. Part I: SOLUTION STOICHIOMETRY
Chapter Four:
Part I:
SOLUTION STOICHIOMETRY
AP Chemistry
Ms. Paskowski

2. Water, the Common Solvent
One of the most important substances on earth
Can dissolve many different substances
A polar molecule
4.1

3. Dissolution of a Solid in a Liquid
4.1

4. Nature of Aqueous Solutions
Solute – substance being dissolved
Solvent – liquid water
Electrolyte – substance that when dissolved in water produces a solution that can conduct electricity
4.2

5. Electrolytes
Strong Electrolytes – conduct current very efficiently (bulb shines brightly)
Weak Electrolytes – conduct only a small current (bulb glows dimly)
Nonelectrolytes – no current flows (bulb remains unlit)
4.2

6. Electrolyte Behavior
4.2

7. Chemical Reactions of Solutions
We must know:
Nature of the reaction
Amounts of chemicals present in the solutions
4.3

8. Molarity
Molarity (M) = moles of solute per volume of solution in liters:
4.3

9. Concept Check
Which of the following solutions contains the greatest number of ions?
400.0 mL of 0.10 M NaCl.
300.0 mL of 0.10 M CaCl2.
200.0 mL of 0.10 M FeCl3.
800.0 mL of 0.10 M sucrose.
a) contains mol of ions (0.400×0.10×2). b) contains mol of ions (0.300×0.10×3). c) contains mol of ions (0.200×0.10×4). d) does not contain any ions because sucrose does not break up into ions. Therefore, letter b) is correct.
4.3

10. Let’s Think About It
Draw molecular level pictures showing each solution. Think about relative numbers of ions.
How many moles of each ion are in each solution?
4.3

11. Notice
The solution with the greatest number of ions is not necessarily the one in which:
the volume of the solution is the largest.
the formula unit has the greatest number of ions.
4.3

12. Dilution
The process of adding water to a stock solution to achieve the molarity desired for a particular solution.
Dilution with water does not alter the numbers of moles of solute present.
Moles of solute before dilution = moles of solute after dilution
M1V1 = M2V2
4.3