Acids, Bases, Buffers and pH

Acids and bases, like salts, dissociate in water into electrolytes. Acids and bases can very much change the properties of the solutions in which they are dissolved.

Acids

An acid can be defined as a proton donor or a substance that releases hydrogen ions (H+) into a solution. For example, hydrochloric acid dissociates into hydrogen ion and chloride ion in water as shown in this equation: HCl ---> H+ and Cl-. Notice in the equation that HCl releases the H+.

An atom of hydrogen has only 1 proton and 1 electron, so H+ is a hydrogen atom that has lost its electron and only the proton remains; thus, you may see H+ referred to as a proton. A common medication for acid reflux is a proton pump inhibitor that prevents acid from being pumped into the stomach.

Bases

A base can be defined as a proton acceptor or a substance that can bind H+ in a solution. For example, HCO₃^- can bind to H+ in a solution to make H₂CO₃ as shown in this equation: HCO₃^- + H+ ------> H₂CO₃.

pH

pH is a scale from 0 to 14 and is a measurement of a concentration of H+ in an acid; however, the scale is the opposite of what you may expect (due to its logarithmic basis which we will not discuss here). The stronger the acid, higher the concentration of H+ and the LOWER the pH. Therefore, a solution with a pH of 1 is EXTREMELY acidic!

The stronger the base, the LOWER the concentration of H+, and the HIGHER the pH! Therefore, a solution with a pH of 14 is EXTREMELY basic (alkaline). Both strong acids and strong bases can be damaging to human tissues (something we rely on is an acidic stomach to kill microorganisms and denature proteins).

A neutral pH is a pH of 7 and the solution would not be considered acidic or basic. Our blood has a pH of 7.35-7.45; therefore it is slightly basic (or alkaline).

Buffers

In humans, the pH of the blood is 7.35-7.45 under healthy conditions. This tight window must be maintained despite constant additions of acids or bases. Buffers resist changes in pH and therefore help stabilize pH. Blood has several types of buffers in order to ensure a mostly stable pH.