Acids and Bases

What is an acid? An acid is a solution that has an excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour". The more H + ions, the more acidic the solution.

Acids Substances that donate hydrogen ions (H + ) to water to form H 3 O + Called the hydronium ion HCl hydrochloric acid used in pools H 2 SO 4 sulfuric acid- battery acid HC 2 H 3 O 2 acetic acid- vinegar HC 6 H 7 O 7 citric acid- lemons, limes

Properties of an Acid Tastes Sour Conduct Electricity Corrosive, which means they break down certain substances. Many acids can corrode fabric, skin, and paper Some acids react strongly with metals and form H+ Turns blue litmus paper red Picture from BBC Revision Bites ases_1.shtml ases_1.shtml

Acids The ones in food are dilute Concentrated acids are dangerous They can burn you skin and eyes Strong acids ionize completely All the H’s make hydronium HCl + H 2 O  Cl - + H 3 O + Makes lots of ions Are dangerous

Acids Weak acids only partially ionize Only a few H’s attach to water HC 2 H 3 O 2 + H 2 O C 2 H 3 O H 3 O + Can be dangerous if concentrated

Uses of Acids (list 3 Examples) Acetic Acid = Vinegar Citric Acid = lemons, limes, & oranges. It is in many sour candies such as lemonhead & sour patch. Ascorbic acid = Vitamin C which your body needs to function. Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. Car batteries

What is a base? A base is a solution that has an excess of OH- ions. Another word for base is alkali. Bases are substances that can accept hydrogen ions

Bases Increases the amount of OH - in solution Either has OH - in it Or takes an H off of water KOH - in drain cleaner NaOH - in drain cleaner NH 3 - ammonia

Properties of a Base Feel Slippery Taste Bitter Corrosive Can conduct electricity. (Think alkaline batteries.) Do not react with metals. Turns red litmus paper blue.

Bases KOH  K + + OH - Strong bases ionize completely Make lots of ions Are dangerous NH 3 + H 2 O NH OH - Weak bases only make a few ions Are dangerous if concentrated

Uses of Bases (List 3 Examples) Bases give soaps, ammonia, and many other cleaning products some of their useful properties. The OH- ions interact strongly with certain substances, such as dirt and grease. Chalk and oven cleaner are examples of familiar products that contain bases. Your blood is a basic solution.

pH Scale pH is a measure of how acidic or basic a solution is. The pH scale ranges from 0 to 14. Acidic solutions have pH values below 7 A solution with a pH of 0 is very acidic. A solution with a pH of 7 is neutral. Pure water has a pH of 7. Basic solutions have pH values above 7.

pH Scale A change of 1 pH unit represents a tenfold change in the acidity of the solution. For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second— it is ten times more acidic.

Acid – Base Reactions A reaction between an acid and a base is called neutralization. An acid- base mixture is not as acidic or basic as the individual starting solutions.

Neutralization Reactions Acids and bases react and neutralize each other Strong acids make lots of ions HCl + H 2 O  H 3 O + + Cl - Strong bases make lots of ions NaOH  Na + + OH - and H 3 O + + OH -  2H 2 O

Neutralization Reactions Put acids and bases together H 3 O + + Cl - + Na + + OH -  Cl - +Na + +2H 2 O The Na + and Cl - make salt which is neutral Water is neutral All ionic compounds are salts Will be neutral if the right amounts of strong acids and bases are added

Neutralization Reactions Weak bases will neutralize a strong acid, but not as well. You need to add more of them If you add enough, it will make the solution basic Same works for weak acids and strong bases As you add acid to a base the pH drops As you add base to and acid the pH rises

Acid – Base reactions Each salt listed in this table can be formed by the reaction between an acid and a base.

Soap Water and oil don’t mix Water is polar Oil is nonpolar Soap can dissolve in both oil and water Made by mixing fats with lye (NaOH)

Soap CO-O- CH 3 CH 2 O-O- O-O-

Soap Hydrophobic non-polar end CO-O- CH 3 CH 2 O-O- O-O-

Soap Hydrophilic polar end CO-O- CH 3 CH 2 O-O- O-O-

CO-O- CH 3 CH 2 O-O- O-O- _

A drop of grease in water Grease is non-polar Water is polar Soap lets you dissolve the non-polar in the polar.

Hydrophobic ends dissolve in grease

Hydrophilic ends dissolve in water

Water molecules can surround and dissolve grease. Helps get grease out of your way.

Detergents Soaps react with minerals in hard water and form scum that doesn’t dissolve Detergents have the same basic structure but have a sulfur at the end, And start from petroleum Dissolve in hard water

Ammonia NH 3 dissolved in water makes a weak base NH 3 + H 2 O NH OH - The OH - ion reacts with grease and makes an emulsion which can wash away Slippery

Household Uses (List 3 Examples) Antacids- Weak bases that neutralize excess stomach acid Shampoo- made from detergents Need to keep pH between 5 and 8 or it will make the hair dull Citric acid keeps fruit from browning Acidic marinades tenderize meats Drain cleaners are strong bases