Acid-Base Theories

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Arrhenius Acids and Bases Acid produces hydrogen ions (H ) in solution Base produces hydroxide ions (OH ) in solution HA ---> H+ + A¯ XOH ---> X+ + OH¯

Arrhenius Examples NaOH  OH-(aq) + Na+(aq) HCl (g)  H+ (aq) + Cl- (aq) HSO4− → H+(aq) + SO42−(aq) Ba(OH)2  2OH-(aq) + Ba2+(aq)

Neutralization Reactions Classified by Arrhenius! We get water and salt in a neutralization reaction

Bronsted-Lowry Acids and Bases An acid is a hydrogen ion (H ) donor A base is a hydrogen ion (H ) acceptor NH3(aq) + HC2H3O2(aq)  NH4+(aq) + C2H3O2-(aq) B/L base B/L acid H2O(l) + HC2H3O2(aq)  H3O+(aq) + C2H3O2-(aq) B/L base B/L acid NH3(aq) + H2O(l)  NH4+(aq) + OH-(aq) B/L base B/L acid

Bronsted-Lowry Examples HCl + H2O  H3O+ + Cl- H2SO4 + H2O  H3O+ + HSO4- HCl + OH-  H2O + Cl-

Lewis Acids and Bases An acid is an electron pair acceptor A + :B → A—B A base is an electron pair donor Once you say that an acid is an electron pair acceptor, then you're not limited to the idea that an acid has to be a hydrogen ion or some chemical that contains or releases hydrogen ions. It could be something else, as long as it can accept (or bond to) a pair of electrons.

Lewis Examples   H+ + :NH3 → NH4+

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

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. Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. Car batteries

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.

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.

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.

How can we identify strong acids or bases? Easy, memorize them! Strong Acids and Bases How can we identify strong acids or bases? Easy, memorize them! Memorized Strong Acids HClO4 H2SO4 HI HBr HCl HNO3 Memorized Strong Bases Hydroxides of group 1 and 2 metals, excluding Be and Mg

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.

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

Monoprotic and Polyprotic Acids Monoprotic can donate one hydrogen ion HCl + H2O → H3O+ + Cl− Diprotic can donate two hydrogen ions H2SO4 Polyprotic is a general term for any acid that can donate more than one hydrogen ion

Examples of polyprotic acids Example: phosphoric acid H3PO4(s) + H2O(l)  H3O+(aq) + H2PO4−(aq) H2PO4−(aq)+ H2O(l)  H3O+(aq) + HPO42−(aq) HPO42−(aq)+ H2O(l)  H3O+(aq) + PO43−(aq)