Acids and Bases: 8.3 and 8.4 Notes

Identifying Acids An acid is a compound that produces hydronium ions (H3O+) when dissolved in water. Acids are also known as proton donors HCl + H2O  H3O+ + Cl- New solution of hydrochloric acid with new properties.

Some Common Acids Acetic Acid  Vinegar Carbonic Acid  Carbonated Beverage Hydrochloric Acid  Digestive Juices Nitric Acid  Fertilizer Production Sulfuric Acid  Car Batteries

General Properties of Acids Sour taste Ex. Lemons, limes, grapefruits have citric acid. Reactivity with metals Ex. Aluminum foil covered container of spaghetti sauce turns dark and develops holes. Ability to produce color changes in indicators. Ex. Common indicator: litmus paper

Identifying Bases A Base is a compound that produces hydroxide ions (OH-) when dissolved in water. Bases are also known as proton acceptors NaOH  Na+ + OH- New solution of Sodium Hydroxide with new chemical properties.

General Properties of Bases Bitter taste Ex. Unsweetened chocolate has the base theobromine Slippery feel Ex. Wet soap contains bases Ability to produce color changes in indicators. Bases do not usually react with metals.

Natural Indicators An indicator is any substance that changes color in the presence of an acid or base. Some flowers like hydrangeas contain natural indicators. The color of the flower depends on whether the plant is growing in acidic or basic soil. Acidic  Bluish purple Basic  Pink

Neutralization Neutralization is a reaction between an acid and a base. A neutralization reaction between an acid and a base produces a salt and water.

Strength of Acids and Bases The pH scale is a scale from 0 to 14 to describe the concentration of hydronium ions in solution. A pH of 7 is neutral. A pH of less than 7 is acidic. A pH of more than 7 is basic.

pH Scale The lower the pH value, the greater the H3O+ ion concentration in the solution. The higher the pH value, the lower the H3O+ ion concentration in the solution. What is the pH of pure water?

Strong Acids Vs. Strong Bases When strong acids dissolve in water, they ionize completely. When strong bases dissolve in water, they dissociate completely.

Weak Acids Vs. Weak Bases Weak acids and bases ionize or dissociate only slightly in water.

Buffers A buffer is a solution that is resistant to large changes in pH. A buffer can react with both an acid or a base while its pH remains relatively constant. Buffers in your body help to keep you at your optimum pH.

Electrolytes An electrolyte is a substance that ionizes or dissociates into ions when it dissolves in water. Electrolytes can conduct electric current. Electrolytes in sports drinks help you to restore the balance of ions in your body. Strong acids and bases are strong electrolytes because they dissociate or ionize almost completely in water.

Acids and Bases video