Families of Chemical Compounds Acids and Bases Families of Chemical Compounds

Acids and Bases Compounds are classified into families based on their chemical and physical properties. The groups of compounds known as acids and bases play an important role in your daily life.

Properties of Acids All acids taste sour. (do not try) All acids change litmus paper from blue to red (This is how you can tell you have an acid). Acid reacts with some metals to produce hydrogen gas. Acids react with bases to produces salts and water. Some acids conduct electric current.

Acid Nomenclature A Binary Acid is one that contains only two different elements. To Name a binary acid takes three rules: 1. Begin with the prefix hydro. 2. The root of the name of te second element. 3. The name then ends with –ic.

Some Common Acids Binary HF – Hydrofluoric acid HCl- Hydrochloric HBr- Hydrobromic Industrial Sulfuric- H2SO4 Nitric- HNO3

Arrhenius Acid- The first definition of an acid. In water Arrhenius acids produce positive hydrogen ions (H+). So acids are often defined as proton (H+) donors. HCl + H2O  H3O+ + Cl -

Properties of Bases Bases usually taste bitter and are slippery to the touch. Bases turn litmus paper from red to blue. Bases react with acids to produce salt and water. Bases conduct electric current.

Arrhenius Base- The first definition of a base In water, Arrhenius bases produce the hydroxide ion (OH-). a base is often defined as a proton acceptor. NaOH + H2O  Na+ + OH -

The pH Scale Solutions can either be basic, acidic or neutral. The pH scale is used to measure the acidity of a solution. The pH scale is a series of numbers from 1-14. A solution with pH below 7 is an acid. A solution with a pH above 7 is a base. A solution with a pH exactly 7 is neutral. Neutral solutions are neither acid nor base

The pH scale

Formation of Salts When acids react chemically with bases, they form water and a class of compounds called salts. These reactions are called neutralizations because they bring pH to 7. H+Cl- + Na+ OH-  H2O + NaCl Acid Base Water Salt

Strength of Acids A strong acid is one that ionizes completely in water. HCl + H2O  H+ + Cl - A weak acid is one that does not ionize completely. HCN + H2O  H+ + CN - 

Strength of Bases A strong base is one that ionizes completely in water. NaOH + H2O  Na+ + OH- A weak base is one that does not ionize completely. NH3 + H2O  NH4+ + OH - 

Bronsted-Lowey Acids and Bases Bronsted-Lowery acid is a molecule or ion that is a proton donor. Bronsted-Lowery base is a molecule or ion that is a proton acceptor.

Conjugate Acids and Bases The Bronsted-Lowery definitions and acids and bases provide a basis for studying proton transfer. HF+ H2O  H3O+ + F –

Conjugate Acids and Bases HF + H2O  H3O+ + F – Acid Conjugate base What remains after a BL acid has given up a proton is the conjugate base. HF + H2O  H3O+ + F – Base Conjugate acid What is formed when a BL base gains a proton is the conjugate acid.