Acids & Bases

I. Water pH is neutral A. We know that water is a polar molecule composed of oxygen and hydrogen. B. We also know that water is a great solvent since it is charged and always can dissolve solutes that have a slight charge C. Water can also be considered to be a hydrogen ion (H⁺) and a hydroxide ion (OH⁻). – 1. One water molecule in about 550 million reacts and forms these ions

I. Water pH is neutral D. Because the number of positive hydrogen ion (H⁺) equals the number of negative hydroxide ion (OH⁻) water is neutral.

II. The pH Scale A. pH scale is a measurement system that indicates the concentration of H⁺ ions in a solution. B. The scales reads from 1-14 – 1. pH of 7 has equal number of H⁺ and OH⁻. – 2. pH of less than 7 is acidic and has more H⁺ than OH⁻ – 3. pH of more than 7 is basic and has more OH⁻ than H⁺

II. The pH Scale cont. C. The lower the number the more acidic the solution is; the higher the number the more basic the solution is. – Strong acids pH = 1-3, Strong bases pH = D. Each step on the pH scale represents a factor of 10. – 1. pH of 4 has 10 times the number of H⁺ than a pH of 5

Acids release H⁺ in the solution Bases release OH⁻ in the solution

An increase in H + ions causes a decrease in pH

III. Characteristics A. Acids are usually sour in taste – Ex. Lemons – composed of citric acid B. Bases are alkaline and have a slippery consistency. – Ex. Common house soap

Litmus Paper

IV. Buffers A. Our cells need to be at a constant pH of 6.5 to 7.5 if it changes drastically the chemical reactions that take place would be greatly effected. B. Controlling the pH is very important to maintain homeostasis. C. Buffers are weak acids & bases that react with strong ones to prevent drastic changes – Example: Ammonium hydroxide & Acetic acid