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ACIDS AND BASES
Sections 8.3 and 8.4
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)
Properties of acidsTASTE SOUR
Things like lemons and oranges, taste sour because they contain acids. Do not test solutions by taste.
REACTIVE WITH METALSA metal changes color when exposed to a substance or bubbles form in a acid when a metal is placed in it.
CHANGE COLORS IN INDICATORSAn indicator is a substance that changes color in the presence of an acid or a baseOne 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.
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.
PROPERTIES OF BASESBITTER TASTE
Cough syrup has a base. Unsweetened (cooking) chocolate has a base in it to make it taste bitter.Again don’t test unknown substances by taste.
SLIPPERY FEELThink 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.
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 -)
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
Buffers and electrolytes
A Buffer is a solution that doesn’t 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
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.