Introduction/Background

     Acids and bases are two classes of compounds that are related to each other and are very important to our daily lives. Some common acids are vinegar (acetic acid) and vitamin C (citric acid). Some bases are lye (sodium hydroxide) and baking soda (sodium bicarbonate). Acid rain is formed when gaseous pollution from cars exhaust mixes with clouds to yield acidic sulfurous acid. This acid is then released when it rains. Bases taste bitter and are usually used as strong cleaning agents. Acids taste sour and are in many foods.

     Acids are compounds that turn litmus paper red, taste sour, and dissolve metals. Bases turn litmus paper blue, taste bitter, and feel slippery, like soap (a very common base), on the skin. An acid and base react together to ALWAYS form water and salts.

Key Concepts

     There are several chemical definitions of acids and bases. There is the Arrhenius definition, which states that an acid is defined as a substance which ionizes in aqueous solution to yield hydrogen ions (H⁺). The Lewis definition of a base states that a base is a substance that acts as an electron pair donor, and an acid is an electron pair acceptor. However, for our purposes, we'll be utilizing the Bronsted-Lowry definition of acids and bases. This definition states that an acid is a proton (H⁺) donor, and a base is a proton acceptor.

     The concept of an acid/base titration is actually rather simple. A base is added to an acid that has had an indicator added to it. At first there will be more of the acid than the base. The base reacts with the protons that are attached to the acid. More base is added until all the protons on the acid have been reacted. This point is called the equivalence point. When more base is added to the acid/indicator mixture, and since there are no more H⁺ ions for the acid to react, the base begins reacting with the H⁺ ions attached to the indicator. The indicator's job is to give a visual representation (in the form of a color change) of the endpoint; the point at which H⁺ ions from the indicator are now reacting with the base. Let's do a couple of examples.

     Next we need to learn how to do some calculations often associated with titrations. Titrations are used to determine the concentration of a substance in solution by adding it to a standard of known concentration until a reaction occurs (usually shown by a color change). One calculation involves calculating the number of moles.

Glossary

     
Conductivity = the quality or power of conducting or transmitting.

Electrolyte = a substance that when dissolved in a suitable solvent or when fused becomes an ionic conductor.

Non-Electrolyte = a substance that does not readily ionize when dissolved or melted and is a poor conductor of electricity.

Solvent = a liquid substance capable of dissolving other substances; "the solvent does not change its state in forming a solution"

Solute = a dissolved substance.

Dilute = reduce in strength or concentration or quality or purity
     

Related Materials

For more about calculations:
     A Few Examples (http://www.chemtutor.com/acid.htm#math)

For more about acids and bases:
     Acids and Bases (http://www.chemtutor.com/acid.htm)