ACIDS AND BASES

1
ACIDS AND BASES

• Sections 8.3 and 8.4

2
Acids

• A acid is a compound that produces hydronium
  (H3O) ions when dissolved in water.
• Examples
• HCl hydrochloric acid
• HNO3 nitric acid
• H2SO4 sulfuric acid
• (Notice the hydrogen in the front)

3
Properties of acids

• TASTE SOUR
• Things like lemons and oranges, taste sour
  because they contain acids.
• Do not test solutions by taste.
• REACTIVE WITH METALS
• A metal changes color when exposed to a substance
  or bubbles form in a acid when a metal is placed
  in it.
• CHANGE COLORS IN INDICATORS
• An indicator is a substance that changes color in
  the presence of an acid or a base
• One type of indicator is Litmus paper. Litmus is
  a dye made from plants.
• Blue litmus turns red in the presence of an acid.
• Red Litmus stays red in the presence of an acid.

4
BASES

• A BASE is a compound that produces hydroxide
  (OH-) ions when dissolved in water
• Examples
• NaOH sodium hydroxide
• Mg(OH)2 magnesium hydroxide
• Ca(OH)2 calcium hydroxide
• Notice the (OH) in each.

5
PROPERTIES OF BASES

• BITTER TASTE
• Cough syrup has a base. Unsweetened (cooking)
  chocolate has a base in it to make it taste
  bitter.
• Again dont test unknown substances by taste.
• SLIPPERY FEEL
• Think about soap when it gets wet.
• CHANGES COLORS IN INDICATORS
• Bases turn red litmus paper blue. Blue litmus
  stays blue.
• Phenolphthalein is another acid and base
  indicator. It turns red in base and stays clear
  in an acid.

6
ACID-BASE REACTIONS

• A reaction between an acid and a base is called
  NEUTRALIZATION.
• The reactants are an acid and a base.
• The products are water and a salt (contains a
  halogen)
• An acid loses its hydrogen ion and is called a
  proton donor (b/c H).
• A base loses its (OH) and is a proton acceptor
  (b/c OH -)

7
pH Scale

• The pH is the measure of Hydronium ions in a
  substance
• Ranges from 0-14
• Low pH (0-6.99) is acidic.
• High pH (7.01 -14) is basic
• 7 is neutral

8
Buffers and electrolytes

• A Buffer is a solution that doesnt allow big
  changes in pH.
• Made from weak acids and weak bases.
• An electrolyte is a substance that ionizes or
  separates into ions when it dissolves in water.
• Made from strong acids or bases.
• Found in sports drinks

9
Strong and weak acids, bases

• Strong acids dissolved in water, ionize almost
  completely.
• Ph is low.
• Strong bases dissolved in water, dissociate
  almost completely.
• Ph is high.
• Weak acids and bases ionize or dissociate
  slightly in water.
• Ph is near neutral.