Transcript Acids and Bases

Acids and Bases
Acids: often have a tart or sour taste
- Examples include citrus fruits, vinegar, carbonated
beverages, car batteries
Properties of Acids:
1. sour/tart taste
2. Aqueous solutions are electrolytes (conduct electricity)
3. Cause indicators to change color
4. Many metals react with acids to produce hydrogen gas
5. React with hydroxides (bases) to produce water and a
salt (ionic compound)
Properties of Bases:
1. React with acids to form water and a salt
2. Taste bitter
3. Feel slippery
4. Bases will change colors of indicators
5. Aqueous solutions conduct electricity
6. Strong bases are extremely caustic to the skin and can
cause deep, painful slow healing wounds
Examples of common bases are antacid tablets, household
cleaning supplies (soap, detergent, ammonia, windex,
...)
Names and Formulas of Acids and Bases
Acid: compound that produces hydrogen ions in water.
- The general formula of an acid is HX where X is a
monatomic or polyatomic anion.
- You must know the formulas and names of the following
acids
HCl – hydrochloric acid
HNO3 – nitric acid
H3PO4 – phosphoric acid
H2SO4 – sulfuric acid
Bases: a compound that produces hydroxide ions (OH-)
when dissolved in water. They are named as
you would name ionic compounds.
- Examples you must know
NaOH – sodium hydroxide
Ca(OH)2 – calcium hydroxide
KOH – potassium hydroxide
When acids and bases react the products will be water and a
salt.
HCl + NaOH → NaCl + H2O
Water can act like an acid or a base:
Water can self ionize or break up to form positive and
negative ions.
H2O → H+
Water
hydrogen ion
2 H2O → H3O+
Water
+ OHHydroxide ion
+ OH-
Hydronium ion
Hydroxide ion
Hydrogen ions are also called protons. The term hydrogen
ion and hydronium ion are used interchangeably.
How pH is calculated
pH: a measure of the concentration of hydrogen ions in a
solution.
- pH is measured on a 0 to 14 scale. 0 being very acidic
and 14 being very basic
In pure water, there are an equal number of hydrogen and
hydroxide ions because each water molecule breaks
into one hydrogen ion and one hydroxide ion
- [H+] = [OH-] in pure water
- In any solution [H+] x [OH-] = 1.0 x 10-14
- pH = -log [H+]
- pOH = -log [OH-]
- pH + pOH = 14 (for all solutions)
- Neutral = 7
- Acidic: 0 < pH < 7
Basic: 7< pH < 14
- See page 602 in your book
Measuring pH
- Measuring pH is use for many applications (swimming pools,
soil acidity for plant growth, medical diagnosis, ect.)
Indicators: a substance that changes color in the presence of
an acid or a base because its acid form is a
different color than this base form.
- The color is compared to a reference chart for that
indicator in order to determine the pH of the
solution.
- For precise and continuous measurements of pH
a pH meter is used
pH meters: uses an electrode in which the voltage of the
electrode changes with the hydrogen ion
concentration of the solution.
- See page 590 in your book
Acid-Base Theories
Arrhenius Acids: acids are hydrogen containing
compounds that ionize to produce hydrogen ions
when dissolved in water.
Arrhenius Base: compounds that ionize to yield hydroxide
ions when dissolved in water.
Monoprotic Acids: compounds that have one ionizable
hydrogen ions (HCl)
Diprotic Acids: compounds that have two ionizable hydrogen
ions (H2SO4)
Triprotic Acids: compounds that have three ionizable
hydrogen ions (H3PO4)
Bronsted-Lowry Acids and Bases
Bronsted-Lowry Acid: Hydrogen ion donor
Bronsted-Lowry Base: hydrogen ion acceptor
All Arrhenius acids and bases are also Bronsted-Lowry
acids and bases, but not vice versa
Conjugate Acid: the particle formed when a base gains a
hydrogen ion.
Conjugate Base: the particle that remains when an acid
has donated a hydrogen ion.
Conjugate Acid-Base Pair: two substances related by the
loss or gain of a single hydrogen ion.
2 HCl + Ca(OH)2 → CaCl2
Acid
+
2 H2O
Base
Conjugate Conjugate
Base
Acid
Amphoteric: a substance that can act as an acid or a base.
- Water is a amphoteric because it can act as an
acid or a base depending on the type of
reaction
Lewis Acids or Bases
Lewis Acid: substance that can accept a pair of electrons to
form a covalent bond.
Lewis Base: substance that can donate a pair of electrons to
form a covalent bond.
- Table 20.6 page 598
Strengths of Acids and Bases
For a list of Strong and Weak Acids and Bases
see table 20.7 on page 600