Acids & Bases

1. Acids & Bases They are everywhere.. In your food In your house EVEN IN YOU!!!!!

2. 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.

3. 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 • Turns blue litmus paper red Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml

4. Naming Acids • Binaryacids – an acid that contains only TWO different elements: • Hydrogen • An electronegative element (F, Cl, Br, I) • Examples: • HF, HCl, HBr, HI • Nomenclature: • Prefix –hydro • Root name of the second element follow the prefix • Suffix –ic • Hydrofluoric acid • Hydrochloric acid

5. Naming Acids • Oxyacid – compound of hydrogen, oxygen and a nonmetal • Usually hydrogen followed by a POLYATOMIC ion (oxyanion) • Examples: • HNO3 – nitric acid (from nitrate) • HClO – hypochlorous acid (from hypochlorite) • TABLE 2: Names of Common Oxyacids and Oxyanions

6. Uses of Acids • 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. • Sulfuricacid is used in the production of fertilizers, steel, paints, and plastics. • Car batteries

7. 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

8. 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.

9. Uses of Bases • 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.

10. General rules • Acids start with an H (HCl, H2SO4) • Bases have an OH in the formula (hydroxide)

11. pH Scale • pHis 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.

12. 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.

13. Calculating pH • pH = - log [H3O+] • ** The more H3O+ ions a solution contains, the more acidic the solution. • Example: A neutral solution has a [H3O+] of 1 x 10-7M • pH = - log (1 x 10-7M) = -(-7.0) = 7.0 • pOH = - log [OH-] • ** The higher the OH- concentration, the more basic a solution is. • Example: A neutral solution has a [OH-] of 1 x 10-14M • pOH = - log (1 x 10-14M) = -(-14.0) = 14.0

14. Arrhenius Acids and Bases • Arrhenius Acid – chemical compound that increases the concentration of hydrogen ions (H+) in an aqueous solution • Arrhenius Base – substance that will increase the concentration of hydroxide ions (OH-) in an aqueous solution • Strong acid/base – one that ionizes completely in aqueous solution (electrolytes) • Weak acid/base – release few ions into the solution (do NOT completely ionize)

15. Brønsted-Lowry Acids and Bases • Brønsted-Lowry Acid – a molecule/ion that is a proton DONOR • Because H+ is a proton – all Arrhenius acids are Brønsted-Lowry acids as well • Brønsted-Lowry Base – a molecule/ion that is a proton ACCEPTOR • The Arrhenius bases are NOT Brønsted-Lowry bases • Brønsted-Lowry Acid-Base Reaction – protons are transferred to from one reactant (the acid) to another (the base)

16. Lewis Acids and Bases • Lewis acid – an atom/ion/molecule that is an electron pair ACCEPTOR • Lewis base – an atom/ion/molecule that is an electron pair DONOR • Lewis Acid-Base Reaction– the formation of one or more covalent bonds between an electron-pair donor and acceptor

17. Acid-Base Reactions • Conjugate Base: • The species that remains after a Brønsted-Lowry Acid has given up a proton HF (aq) + H2O (l)  F-(aq) + H3O+(aq) (acid) (base)(conj. base) (conj. acid) • Conjugate Acid: • The species that is formed after a Brønsted-Lowry base gains a proton

18. Acid – Base Reactions • A reaction between an acid and a base is called neutralization. • Neutralization produces a SALT and WATER. An acid-base mixture is not as acidic or basic as the individual starting solutions. • Acid plus base yields salt and water.

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

20. Water • Water (H2O) can be both an acid and a base, depending on how you look at it. It can be considered an acid in some cases and a base in others. Water can even react with itself to form acids and bases. It happens in really small amounts. The pH isn’t affected because the amounts of ions are small.It goes like this: 2H2O --> H3O+ + OH- • H3O+ is called a hydronium ion • OH-is called a hydroxide ion • This process is referred to as the self-ionization of water.