1. Unit 4: Acid-Base Theory
Lesson 5: Strong and Weak Acids and Bases

2. “Strong” and “Weak” A strong acid or base is 100% ionized in solution.
Strong acids and bases undergo neutralization reactions.
A weak acid or base is less than 100% ionized in solution.
Weak acids and bases undergo equilibrium reactions.
5 min

3. Strong vs. Concentrated
Demo: Reaction of magnesium with:
a) 50 mL of 1.0 M hydrochloric acid
b) 50 mL of 1.0 M acetic acid
Which reaction will be faster (if any)?
Weak and strong refer to the percentage of ionization.
Dilute and concentrated refer to the molarity of a solution.
12.IV.2 – 10 min
Don’t bother trying to light H2 gas – there isn’t enough of it produced.

4. Brain Break!

5. Strong Acids and Bases
The strong acids are the top six acids on the left side of the “Relative Strengths” table.
The strong bases are
the bottom two bases
on the right side of the
table, as well as metal
hydroxides (e.g. NaOH,
Ca(OH)2, KOH).

6. Weak Acids and Bases
The weak acids are on the left side of the “Relative Strengths” table, from HIO3 down to H2O.
The weak bases are on the right side, from H2O down to PO43-.
The weak acids on the left are separated by equilibrium arrows from their conjugate bases on the right.

7. Using the Relative Strengths Table
The higher an acid is on the left side, the stronger the acid.
The lower a base is on the right side, the stronger the base.
The stronger an acid, the weaker its conjugate base, and vice versa.

8. Acids and Bases in Water
When acids dissolve in water, they form H3O+.
E.g. HCl + H2O → H3O+ + Cl- (strong)
H2S + H2O H3O+ + HS- (weak)
When bases dissolve in water, they form OH-.
E.g. NH2- + H2O → NH3 + OH- (strong)
H2O + HS H2S + OH- (weak)

9. Homework:
Pg. 125 #21, 22, and 24
10 min