1. Chapter 19: Acids & Bases

2. Properties of Acids & Bases
Acid: substance dissociates to form H+ in solution
Tastes sour
Feels sticky
Conductor of electricity
Turns blue litmus red
Example: HCl
Base: substance dissociates to form OH- (hydroxide) in solution
Tastes bitter
Feels slippery
Turns red litmus blue
Example: NaOH

3. Arrhenius Model Arrhenius model: HCl ionizes to produce H+ ions.
Traditional definition for acids and bases
States that an acid is a substance that contains hydrogen and ionizes to produce hydrogen ions in aqueous solution, and a base is a substance that contains a hydroxide group and dissociates to produce a hydroxide ion in solution.
HCl ionizes to produce H+ ions.
HCl(g) → H+(aq) + Cl–(aq)
NaOH dissociates to produce OH– ions.
NaOH(s) → Na+(aq) + OH–(aq)
* Some solutions produce hydroxide ions even though they do not contain a hydroxide group.

4. The usual solvent for acids and bases is water— water produces equal numbers of hydrogen and hydroxide ions in a process called self-ionization.
H2O(l) ↔ H+(aq) + OH–(aq)
In reality: H2O(l) + H2O(l) ↔ H3O+(aq) + OH–(aq)
The hydronium ion is H3O+. The symbols H+ and H3O+ can be used interchangeably.

5. Brønsted-Lowry Model Brønsted-Lowry Model:
More general definition for acids and bases
States that an acid is a hydrogen ion donor and a base is a hydrogen ion acceptor
** NH3 is a Brønsted-Lowry base, but not an Arrhenius base
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
- H2O (acting as an acid) donates a proton to ammonia
- NH3 (acting as a base) accepts a proton from water
Conjugate acid: the species produced when a base accepts a hydrogen ion
(NH4+ in the above reaction)
Conjugate base: the species produced when an acid donates a hydrogen ion
(OH- in example)
Conjugate acid-base pair: consists of two substances related to each other by donating and accepting a single hydrogen ion

6. Hydrogen fluoride—a Brønsted-Lowry acid
HF(aq) + H2O(l) ↔ H3O+(aq) + F–(aq)
HF = acid, H2O = base,
H3O+ = conjugate acid, F– = conjugate base

7. HNO2 (aq) + H2O (l)  NO2- (aq) + H3O+ (aq)
Water and other substances that can act as acids or bases are called amphoteric.

8. Monoprotic and Polyprotic Acids
Monoprotic Acid: an acid that can donate only one hydrogen ion
Only ionizable hydrogen atoms can be donated
Polyprotic Acid: an acid that can donate more than one hydrogen ion

10. Strength of Acids
Strong Acids: acids that ionize completely
Because they produce the maximum number of hydrogen ions, strong acids are good conductors of electricity
Conjugate bases are usually weak
HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
Weak Acids: acids that ionize only partially in dilute solutions

11. Strength of Bases
Strong Base: a base that dissociates completely into metal ions and hydroxide ions
Alkali metals or heavier alkaline earth metals
Weak base: ionizes only partially in dilute aqueous solution

12. pH pH scale: measure of the acidity of an aqueous solution
Concentrations of H+ ions are often small numbers expressed in exponential notation
pH is the negative logarithm of the hydrogen ion concentration of a solution. Changing [H+] by a factor of 10 causes the pH to change by 1 unit
pH = -log [H+]
- Litmus paper and a pH meter with electrodes can determine the pH of a solution.

13. pOH
pOH of a solution is the negative logarithm of the hydroxide ion concentration
pOH = -log [OH-]
The sum of pH and pOH equals 14

14. Practice Calculate the [H+] and [OH-] when pH = 7.40
Calculate the pH and pOH when [OH-] = 4.0x10-3M

15. Neutralization
A neutralization reaction is a reaction in which an acid and a base in an aqueous solution react to produce a salt and water.
A salt is an ionic compound made up of a cation from a base and an anion from an acid.
Neutralization is a double-replacement reaction.

16. Titrations
Titration is a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration.
In a titration procedure, a measured volume of an acid or base of unknown concentration is placed in a beaker, and initial pH recorded.
A buret is filled with the titrating solution of known concentration, called a titrant.

18. Measured volumes of the standard solution are added slowly and mixed into the solution in the beaker, and the pH is read and recorded after each addition. The process continues until the reaction reaches the equivalence point, which is the point at which moles of H+ ion from the acid equals moles of OH– ion from the base.
An abrupt change in pH occurs at the equivalence point.

20. Chemical dyes whose color are affected by acidic and basic solutions are called acid-base indicators.

21. An end point is the point at which an indicator used in a titration changes color.
An indicator will change color at the equivalence point.

22. Molarity from Titration
** Must have a balanced equation**
Use stoichiometry
A volume of 18.28mL of a standard solution of M NaOH was required to neutralize mL of a solution of methanoic acid (HCOOH). What is the molarity of the acid solution

23. What is the molarity of nitric acid solution is 43. 33 mL of 0
What is the molarity of nitric acid solution is mL of M KOH solution is needed to neutralize mL of the acid solution.

24. How many milliliters of 0. 500 M NaOH would neutralize 25. 00 mL of 0
How many milliliters of M NaOH would neutralize mL of 0.100M H3PO4.