Review: H3PO4 is a polyprotic acid, meaning it has multiple protons to donate when dissociating with water. a. Write Bronsted-Lowry reactions for the 3 successive removals or protons from this acid. a. Which species in the reactions are amphoteric? b. What is the conjugate base in the 2nd reaction? c. What is the equation for the net process after all 3 removals? Hint: cross off intermediates d. If the pH of a H3PO4 solution is 5.37, what is the [OH-]?

Objectives: Understand the difference between a strong and weak acid and/or base. Define acid and base dissociation constants and understand what they indicate.

Strong/Weak Acids and Bases Strong acid or base DOES NOT mean more dangerous or more reactive!!! Hydrofluoric is a great example. HF and glass Breaking Bad Bathtub Scene

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Day 2

Strong/Weak Acids and Bases What are strong acids and bases??? HA (aq) + H2O (l)  H3O+ (aq) + A- (aq) (Strong) 100% of the HA originally added will react 100% dissociation React to completion These are NOT equilibrium processes The same is true for bases that are strong

Strong/Weak Acids and Bases What are strong acids and bases??? HA (aq) + H2O (l)  H3O+ (aq) + A- (aq) (Strong) These are NOT equilibrium processes Ka = acid dissociation constant = K values will be simply listed as “large” for any acid or base that is strong

Strong/Weak Acids and Bases What are strong acids and bases??? HA (aq) + H2O (l)  H3O+ (aq) + A- (aq) (Strong) Complete dissociation Relative amounts Before rxn After rxn

Strong/Weak Acids and Bases

Strong/Weak Acids and Bases What are weak acids and bases??? HA (aq) + H2O (l) ↔ A- (aq) + H3O+ (aq) (Weak) Only some of HA originally added will react Partial (less than 100%) dissociation React partially These ARE equilibrium processes The same is true for bases that are weak

Strong/Weak Acids and Bases What are weak acids and bases??? HA (aq) + H2O (l) ↔ A- (aq) + H3O+ (aq) (Weak) These ARE equilibrium processes Ka = Most acids and bases considered weak are reactant favored and have Ka and Kb values < 1

Strong/Weak Acids and Bases What are weak acids and bases??? HA (aq) + H2O (l) ↔ A- (aq) + H3O+ (aq) (Weak) Partial dissociation Relative amounts Before rxn After rxn

Strong/Weak Acids and Bases

Strong/Weak Acids and Bases The Big Idea: The stronger the acid/base, the more product-favored, the larger the Ka/Kb value

This chart shows some common acids, ranked by strength, and compared to the each acid’s conjugate base

Try and answer the Final Connections questions on the handout Try and answer the Final Connections questions on the handout. Pay special attention to 4 and 6!

1. Which acid is stronger: sulfuric acid or sulfurous acid?

2. Which base is stronger: the nitrite ion or the sulfite ion?

3. Which of the acids from problem 1 has the stronger conjugate base?

4. What is the relationship between the strength of an acid and it’s conjugate base? Strong acids have weak conjugate bases

5. Which acid is stronger: phosphoric acid, dihydrogen phosphate or hydrogen phosphate?

6. How does the strength of an acid change as successive hydrogen ions are removed? Acids get weaker as hydrogen ions are removed

Which acid would have the higher acid dissociation constant: HCl or HClO?   Which acid is the stronger acid: HBr or HBrO3? Which base is stronger: the fluoride ion or the chloride ion? 1.0 M solutions of which acid would produce the greater H3O+ concentration in solution: hydroiodic acid or propanoic acid? 1.0 M solutions of which base would produce the greater OH-1 concentration in solution: the bromide ion or the nitrite ion? Which acid is stronger: H2CO3 or HCO3-1?