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Chemistry Project: Acids and Bases & the pH Scale

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Chemistry Project: Acids and Bases & the pH Scale

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  • March 13, 2006
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Acids and Bases are two groups of chemical compounds that generally have opposite

characteristics. They have there own unique traits, acids taste sour, turn litmus red while

bases taste bitter and turn litmus blue. The term pH relates to measuring the acidity or

alkalinity of a solution, such as vinegar, or even a damp substance like soul.

The neutral pH is 7, which is essentially water, with lower numbers indicating acidity and

higher numbers indicating alkalinity. Hydronium ions (H3O+) are formed when water

molecules (H2O) bond with hydrogen ions (H+). Hydronium ions are positively charged

because of their extra hydrogen ion. Hydroxide ions (OH-) are produced when water

molecules (H2O) ionize to become hydronium ions (H3O+) and hydroxide ions (OH-).

Substances with a high concentration of hydroxide ions are bases. Bases have a pH rating

of seven or higher. Solutions of ions conduct an electric current, similar in the way that

wire does. Ions can move about in a solution and carry a charge. If they can do carry the

charge they are electrolytes.

The Bronsted-Lowry theory states that an acid is a proton donor and a base a

proton acceptor. Although the acid must still contain hydrogen, the Bronsted-Lowry

theory does not require an aqueous medium. The Bronsted-Lowry definition of acids and

bases also explains why a strong acid displaces a weak acid from its compounds and

likewise for strong and weak bases. In the Lewis theory of acid-base reactions, bases

donate pairs of electrons and acids accept pairs of electrons. A Lewis acid is any

substance, such as the H+ ion, that can accept a pair of nonbonding electrons. Therefore, a

Lewis acid is an electron-pair acceptor. A Lewis base is any substance, such as the OH-

ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an

electron-pair donor.

Svante Arrhenius was a Swedish chemist who helped lay the foundation of

modern day...