Acids, Bases and Indicators on the Molecular Level This paper will present the chemistry behind acids, bases and indicators on the molecular level. The concept of pH and the practical applications of pH indicators will be explained. The structural changes that an indicator undergoes with the change in solution pH will be explored. One of the earliest theories dealing with acids and bases, still useful today, was Arrhenius theory. According to this theory acids are substances that ionize in water to produce hydrogen ions H+ (or protons). Thus, on a molecular basis, it is the H+ cation that gives acidic properties to a solution. An example of such substance is hydrochloric acid, HCl. In water, an HCl molecule dissociates into hydrogen ion H+...The end:
..... an indicator that changes its color at pH = 9.4 ( Hage and Carr 293). Below pH 9.4, phenolphthalein is colorless and has all its protons. However, as pH of solution reaches 9.4, the solution becomes so basic that phenolphthalein acts as a proton donor (an acid). Its molecules loose two protons and the resulting anion is pink in color ( Hage and Carr 293). Works Cited Hage , David S., and James D. Carr. Analytical Chemistry and Quantitative Analysis. Toronto: Prentice Hall- Pearson, 2011. Print. Laird, Brian B. University Chemistry. Boston: McGraw Hill, 2009. Print. Petrucci , Ralph, F. Geoffrey Herring, Jeffry D. Madura , and Carey Bissonnette . General Chemistry: Principles and Modern Applications. 10th ed. Toronto: Pearson Canada. Print.