INTRODUCTION TO ACIDS & BASES Acids & Bases

 Acids and Bases are found in many everyday items, like foods, cleaners, and medicines.  Weak acids are strong bases; strong acids are weak bases.

General Properties  pH below 7  sour taste  react with metals to form H 2 gas  slippery feel  pH above 7  bitter taste ChemASAP  vinegar, milk, soda, apples, citrus fruits  ammonia, lye, antacid, baking soda

Definitions  In aqueous solution… HCl + H 2 O  H 3 O + + Cl – AcidsAcids form hydronium ions (H 3 O + ) H HHHH H Cl OO – + acid

Definitions  In aqueous solution… BasesBases form hydroxide ions (OH - ) NH 3 + H 2 O  NH OH - H H H H H H N NO O – + H H H H base

Types of Acids/Bases Arrhenius Acids/Bases Acids release H + into water Bases release OH - into water Ex: Acid: HCl (aq) H + (aq) + Cl - (aq) Base: NaOH (aq) Na + (aq) + OH - (aq) Monoprotic = acid that contain 1 proton (H + ) Ex.) HBr Diprotic = acids that conatin 2 protons (2H + ) Ex.) H 2 SO 4

Bronsted-Lowry Acids/Bases Acid = Proton H + Donor Base = Proton H + Acceptor o Ex: NH 3 + H 2 O  NH OH - NH 3 - base HOH - acid NH conjugate acid (formed when base gains H + ) – usually positively charged OH - - conjugate base (formed when acid loses an H + ) – usually negatively charged

Proton-Transfer Reactions—Direction and Strength  The extent to which a proton-transfer reaction takes place depends on the strength of the acids and bases involved in the reaction.  Weak acids/bases do not ionize completely, so they tend to re-form in aqueous solution. Therefore, the reactions those compounds undergo with water are reversible.  When a strong acid or base reacts with water in aqueous solution, a non- reversible (single-direction) reaction occurs.  Example: the strong acid HCl ionizes completely in water due to its high polarity once it is broken apart, it does not reform, hence the single-sided arrow pointing to the right.  The reason HCl (and all other strong acids) do not re-form is because the conj. bases they make are very weak and have trouble re-gaining the proton from the conj. acid.  Therefore, when a strong acid (or base) breaks up, it does not re-form again, so we say it “ionizes/dissociates completely.” HCl + H 2 O Cl - + H 3 O + - +

 Two important rules about proton-transfer reactions can be made: 1. The stronger an acid is, the weaker its conj. base will be; the stronger a base is, the weaker its conj. acid will be 2. Proton-transfer reactions tend to favor the production of the weaker acid/base

Acid Nomenclature  Acids are distinguished from other substances by the presence of one or more hydrogen ions (H + ) or hydrogen atoms at the beginning of the formula.  To name an acid correctly, you must know the types of acid it is. There are two types of acids: Binary Acids and Oxyacids  Binary acid = an acid consisting of only 2 elements (hydrogen + nonmetal). To name a binary acid, follow this procedure: 1. Use the prefix “hydro-” 2. Name the element the H is bonded to 3. Take the ending off the element name 4. Add the suffix “-ic” to the element name 5. Add the separate word “acid” to the end HCl a s an example: hydro chlorine hydro chlor - hydrochlor ic hydrochloric acid

Examples

 Oxyacid = an acid consisting of 3 or more elements (hydrogen + polyatomic ion).  To name a oxyacid, follow this procedure: 1. Name the polyatomic ion the H is bonded to 2. Take the ending off the polyatomic ion name 3. Add a suffix to the polyatomic ion name—if the polyatomic ion name ends in: a. “-ite,” use the suffix “-ous” b. “-ate,” use the suffix “-ic” 4. Add the separate word “acid” to the end H 2 CO 3 a s an example: carbonate carbon- carbon ic carbonic acid

Examples