Acids  When an acid dissolves in water, some of the hydrogen is released as hydrogen ions, H +.  An acid is a substance that produces hydrogen ions in a water solution.  When an acid dissolved in water, H + ions interact with water molecules to form H 3 O + ions, which are called hydronium ions.

Properties of Acids  Tart or sour to taste  Electrolytes  Acids also react with indicators to produce predictable changes in color. An indicator is an organic compound that changes color in acids or bases.  Will react with a base to form a salt and water  Examples: vinegar, milk, soda, apples, citrus fruits

Bases  When a base dissolves in water, some of the hydroxide ions (OH - ) are released.

Properties of Bases  Bitter taste  Electrolytes  Change the color of indicators  Will react with an acid to form a salt and water  Slippery/slimy in solution  Examples: ammonia, lye, antacid, baking soda

Water  Water is made of an acid and a base. H 2 0 ↔ H + + OH -  In any aqueous solution [H + ] and [OH - ] are interdependent so when [H + ] increase [OH - ] decreases and vice versa.  Neutralization occurs when an acid & a base react. ○ The products of a neutralization reaction are salt & water.

Aqueous Solutions  Acids form H + or H 3 O + ions. HCl + H 2 O  H 3 O + + Cl –  Bases form hydroxide ions (OH - ). NH 3 + H 2 O  NH OH

Acid and Base Solutions  A neutral solution is any solution where the [H + ] is equal to the [OH - ].  An acidic solution is any solution where the [H + ] is greater than the [OH - ].  A basic solution, also called an alkaline, is where the [OH - ] is greater than the [H + ].

Acid/Bases Strength  Strong Acid/Base 100% ionized in water strong electrolyte - + HCl HNO 3 H 2 SO 4 HBr HI HClO 4 NaOH KOH Ca(OH) 2 Ba(OH) 2

Acid/Bases Strength  Weak Acid/Base does not ionize completely weak electrolyte - + HF CH 3 COOH H 3 PO 4 H 2 CO 3 HCN NH 3

Indicators  Common Indicators: Litmus - ○ Acids turn litmus red. ○ Bases turn litmus blue. pH Meter/Paper: A device or paper used to measure the exact pH of a solution. Phenolphthalein - ○ Colorless in an acid. ○ Very faint pink in a neutral solution. ○ Bright pink in a base.

pH Scale  Expresses the H + ion concentration in a substance.  Acidic solutions have pH values less than 7.  Basic solutions have pH values greater than 7.  Neutral solutions have a pH value equal to 7.

pH = -log[H + ] pH Calculations 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14 pouvoir hydrogène (French) “hydrogen power”

pH Calculations  What is the pH of M HNO 3 ? pH = -log[H + ] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

pH Calculations  What is the pH of 1.0 x10 -7 M? pH = -log[H + ] pH = -log[ 1.0 x10 -7 ] pH = 7 Acidic or basic? Neither

pH Scale Activity  Objective:Create a pH Scale and identify the pH of common substances.  Materials: (Per group set up) 18 inch construction paper Copies of pH pictures Markers/writing utensils Colored pencils Scissors Glue stick

pH Scale

pH Scale Activity  Procedure:  Using the chart or given information, LABEL the pH of each of the attached pictures of common substances.  Neatly draw a pH scale on the construction paper. Scale the line from 0 to 14 with a mark for each number.  Cut and glue the common substances attached at their correct pH on the scale.  Cut and glue the acid/base labels at their correct position on the pH scale.