Acids, Bases & Salts Acids & Bases  Definitions  Properties  Uses

Acids  Acids Substance that produces hydrogen ions in a water solution When an acid dissolves, H + ions interact with water forming hydronium ions (H 3 O + )  Dissociation of Acids: Acid dissolves in water Negative areas of water molecules attract positive hydrogen H + combine with water

HCl + H 2 O  H 3 O + + Cl –

Definitions  Bases Substance that form hydroxide ions (OH - ) in water  Dissociation of Bases: Base containing -OH dissolves in water Negative areas of water molecules attract positive ion in the base Leaving OH -

NH 3 + H 2 O  NH OH - Ammonia

Definitions  Indicator substance that changes color in an acid or base  Examples: litmus - red/blue phenolphthalein - colorless/pink

Properties  sour taste  corrosive  electrolytes  turn litmus red  react with metals to form H 2 gas  bitter taste  corrosive  electrolytes  turn litmus blue  slippery feel

Uses  H 3 PO 4 - soft drinks, fertilizer, detergents  H 2 SO 4 - fertilizer, car batteries  HCl - gastric juice  HC 2 H 3 O 2 - vinegar

Uses  NaOH - lye, drain and oven cleaner  Mg(OH) 2 - laxative, antacid  NH 3 - cleaners, fertilizer

Strong vs. Weak  Strong Acid/Base 100% ions in water strong electrolyte HCl, HNO 3, NaOH, LiOH  Weak Acid/Base few ions in water weak electrolyte HC 2 H 3 O 2, NH

Strong Acids  Strong Acids Nearly all the acid dissociates We use a single arrow Almost all particles are H 3 O + and Cl -

Weak Acids  Weak Acids Only some of the reactants dissociate Most particles are reactants a few are products Use two arrows (it goes back and forth)

Strong Bases  Strong Bases: Dissociates completely in a solution Produces ions (charged particles) One arrow

Weak Bases  Weak Bases: Does not dissociate completely Produces small number of ions Mostly reactants left Two arrows (back and forth)

pH Scale 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14  pH a measure of the concentration of H 3 O + ions in solution measured with a pH meter or an indicator with a wide color range

pH Scale pH of Common Substances

Blood pH  pH of blood must stay between 7.0 and 7.8  Buffers: solutions containing ions that react with acids and bases to minimize pH  Buffers keep blood around a pH of 7.4

Neutralization Reaction  Chemical reaction between an acid and a base.  Products are a salt (ionic compound) and water.

Salt  Salt: Compound formed from negative acid ions and positive base ions  Not always NaCl (Sodium Chloride)

Common Salts

ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H 2 O Neutralization does not always mean pH = 7. = Neutralization Reaction

KOH + HNO 3  H 2 O + KNO 3 Acid? Base? Salt? HNO 3 KOH KNO 3 Neutralization Reaction