Integrated SequencePhysics Chemistry Organic Biology

Web Resources

University of British Columbia - The Common Ion Effect
Excellent series of examples for an important MCAT topic.

Purdue University - How To Adjust the Concentration of an Ion
Excellent example of adjusting pH to control weak electrolyte solubility, a very common type of scenario on the MCAT.

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Special points of emphasis

Chemical Thermodynamics and the Equilibrium State


The solubility of many salts of weak acids (carbonates, phosphates, acetates, sulfides, etc) are dependent on the hydrogen ion concentration. The lower the pH, the higher the solubility because the acid-base equilibrium becomes coupled with the solution process of the electrolyte.

High hydrogen ion concentration drives the formation of the conjugate acid of the anion, which, in turn, reduces the anion concentration in solution. As LeChatelier's principle would predict, this drives the solution process forward. This is why vinegar (acetic acid) can be used to clean calcium carbonate scale from coffee pots.


Acids and Bases


The Respiratory System

Carbon dioxide combines chemically with water to form carbonic acid. Carbon dioxide transport in the blood and tissues involves the complex coupled equilibria between the solubility of carbon dioxide gas in water and the formation of carbonic acid coupled with the diprotic acid-base equilibrium with carbonic acid, carbonate and bicarbonate. Hemoglobin also binds carbon dioxide, so that figures in too.

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