Presentation on theme: "ACIDS AND BASES Sections 8.3 and 8.4. Acids A acid is a compound that produces hydronium (H 3 O + ) ions when dissolved in water. Examples: HCl – hydrochloric."— Presentation transcript:
Acids A acid is a compound that produces hydronium (H 3 O + ) ions when dissolved in water. Examples: HCl – hydrochloric acid HNO 3 – nitric acid H 2 SO 4 – sulfuric acid (Notice the hydrogen in the front)
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.
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 BASES BITTER 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 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.
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.