9.1 Acids and Bases:

Acids Produce Hydronium Ions and Bases produce Hydroxide Ions in Aq Solutions:

1. Arrhenius definition:

   • Acid: produces H3O or hydronium ions. polyatomic ion w/ 3 O-H bonds, has a charge of +1.

   • Bases: hydroxide ion, OH- in a aq solution. They undergo a solvation in water

` Ionic Compounds:

• electrolytes

• Group 1A salts of hydroxide = strong electrolytes & they are soluble in water.

` Ionic Compounds w/ hydroxide ions

• Ex: Mg(OH)2 - magnesium hydroxide

• a base due to producing hydroxide ions in solution

• weak electrolytes

The Bronsted-Lowry Theory of Acids and Bases:

• Bronsted-Lowry Theory:

  1. an acid: donates a proton, H+

  2. a base: accepts a proton from an acid.

     

Acids:

• This is according to Bronsted-Lowry:

  1. water has been added to an acid.

  2. acid will donate a proton to water = this will for a conjugate base

  3. water accepts a proton = forms a hydronium ion

  4. hydronium ion = the conjugate acid of water.

• Conjugate Base: ion or molecule produced when an acid loses a proton

Bases:

• This is according to Bronsted-Lowry Theory:

  1. a base gets water added = a proton from water will be accepted.

  2. water is the acid in this scenario

  3. base + water = hydroxide ion OH- and ammonium ion NH4+.

  4. Conjugate Acid: ion/molecule formed when a base accepts a proton.

  5. Amphoteric Compounds: compounds that can become either an acid or a base.

     

Conjugate Acid-Base Pairs:

• Conjugate acid base pair: can be the pair of

  1. base and its conjugate base

  2. acid and its conjugate base

• determining the structure/formula of conjugate bases:

• Difference between acid-base pairs:

  1. conjugate acid of a base: has 1 more hydrogen, and charge one unit more positive than the base.

How to Identify Them in a Reaction

1. Find the species that loses H⁺ → that’s the acid.

2. Find what that acid becomes after losing H⁺ → that’s its conjugate base.

3. Find the species that gains H⁺ → that’s the base.

4. Find what that base becomes after gaining H⁺ → that’s its conjugate acid.

Common Conjugate Pairs Examples

💡 Helpful Tips

• If it loses H⁺, it’s an acid; the leftover is its conjugate base.

• If it gains H⁺, it’s a base; the result is its conjugate acid.

• The acid and conjugate base always differ by 1 H⁺.

• The base and conjugate acid also differ by 1 H⁺.

• Only strong acid produced in human body = hydrochloric acid HCl