World Journal of Chemical Education. 2017, 5(1), 1-8
DOI: 10.12691/WJCE-5-1-1
Original Research

The Basis of the Limiting Reagent Concept, Its Identification and Applications

Diego J. R. da Silva1,

1Departamento de Química Fundamental Universidade Federal de Pernambuco, Recife, Brazil

Pub. Date: January 21, 2017

Cite this paper

Diego J. R. da Silva. The Basis of the Limiting Reagent Concept, Its Identification and Applications. World Journal of Chemical Education. 2017; 5(1):1-8. doi: 10.12691/WJCE-5-1-1

Abstract

A general formalism for defining and identifying limiting reagent in closed systems is proposed and it is correlated to usual definitions and identification methods. An alternative definition of limiting reagent is proposed, based on real situations after the reaction is complete. Useful equations relating the limiting reagent to products and excess reagents (if the limiting reagent is completely consumed or not) and to reaction yields are given and briefly applied.

Keywords

limiting reagent, stoichiometry, percent yield, excess reagent

Copyright

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References

[1]  Chandrasegaran, A. L., Treagust, D. F., Waldrip, B. G., Chandrasegaran, A., “Students’ dilemmas in reaction stoichiometry problem solving: deducing the limiting reagent in chemical reactions,” Chem. Educ. Res. Pract., 10, 14-23, Nov. 2008.
 
[2]  Toth, Z., “Limiting Reactant: An Alternative Analogy,” J. Chem. Educ., 76(7), 934, Jul.1999.
 
[3]  Silversmith, E. F., “Limiting and Excess Reagents, Theoretical Yield,” J. Chem. Educ., 62(1), 61, Jan.1985.
 
[4]  Phillips, J. C., “A Graphical Representation of Limiting Reactant,” J. Chem. Educ., 71(12), 1048, Dec.1994.
 
[5]  Sostarecz, M. C., Sostarecz, A. G., “A Conceptual Approach to Limiting-Reagent Problems,” J. Chem. Educ., 89(9), 1148-1151, Jul.2012.
 
[6]  Artdej, R., Thongpanchang, T., “Dramatic Classroom Demonstration of Limiting Reagent Using the Vinegar and Sodium Hydrogen Carbonate Reaction,” J. Chem. Educ., 85(10), 1382-1384, Oct.2008.
 
[7]  Kildahl, N., Berka, L. H., “Experiments for Modern Introductory Chemistry: Limiting Reagent, Stoichiometry, and the Mole,” J. Chem. Educ., 70(8), 671-673, Aug.1993.
 
[8]  Zundahl, S. S., Chemical Principles, Houghton Mifflin Company, Boston, 2005, 72-77.
 
[9]  McMurry, J., Fay, R. C., Chemistry, Prentice Hall, New Jersey, 2003, 88-91.
 
[10]  Moog, R. S., Farrell, J. J., Chemistry: A Guided Inquiry, John Wiley & Sons, Inc., New York, 2011, 175.
 
[11]  Silberberg, M. S., Principles of General Chemistry, McGraw-Hill, New York, 2010, 92-98.
 
[12]  Moore, J. T., Langley, R. T., Chemistry for the Utterly Confused, McGraw-Hill, New York, 2007, 36-38.
 
[13]  Ebbing, D. D., Gammon, S. D., General Chemistry, Houghton Mifflin Company, Boston, 2009, 107-112.
 
[14]  Chang, R., Overby, J., General Chemistry: The Essential Concepts, McGraw-Hill, New York, 2011, 83-87.
 
[15]  Whitten, K., Davis, R., Peck, M. L., General Chemistry, Cengage Learning, Boston, 1999, 96-100.
 
[16]  Rosemberg, J. L., Epstein, L. M., Schaum's Outline of Theory and Problems of College Chemistry, McGraw-Hill, New York, 2010, 45.
 
[17]  Goldberg, D. E., Schaum's Outline of Theory and Problems of Beginning Chemistry, McGraw-Hill, New York, 2005, 144-147.
 
[18]  The term “stoichiometric amount of substance” has been used before: see [19], for instance. It is the amount of substance added or subtracted from the system according to this definition. However, I believe the term have a proper use as I propose here, using “stoichiometric amount of substance” to designate the amount of substance “normalized” by its stoichiometric coefficient.
 
[19]  Siggaard-Andersen, O., Durst, R. A., Maas, A. H. J., “Approved Recommendation (1984) on Physico-Chemical Quantities and Units in Chemistry with Special Emphasis on Activities and Activity Coefficients,” J. Clin. Chem. Clin. Biochem., 25(6), 369-391, Jun.1987.
 
[20]  For definitions the symbol ““ is appropriate. See [21].
 
[21]  Cohen, E. R., Cvitas, T., Frey, J. G., Holmström, B., Kuchitsu, K., Marquardt, R., Mills, I., Pavese, F., Quack, M., Stohner, J., Strauss, H. L., Takami, M., Thor, A. J., Quantities, Units and Symbols in Physical Chemistry, IUPAC Green Book, IUPAC & RSC Publishing, Cambridge, 2008, 53, 105.
 
[22]  Reaction extent at time t is defined as and it is always positive, since for reagents and , and for products and . It is frequently used in “equilibrium tables” in the form of (without “t”, mostly), if V is volume. For an advisable reading about its importance and scope, consult [23].
 
[23]  Moretti, G., “The “extent of reaction”: a powerful concept to study chemical transformations at the first-year general chemistry courses,” Found. Chem., 17(2), 107-115, Jul.2014.
 
[24]  Abbott, M. M., Van Ness, H. C., Schaum's Outline of Theory and Problems of Thermodynamics, McGraw-Hill, New York, 1972, 274.
 
[25]  See observation in [22].
 
[26]  Here it is assumed the stoichiometric coefficients do not change through the reaction, or that the reaction has a time-independent stoichiometry. For a brief comment on this matter, consult [27].
 
[27]  Laidler, K. J., Chemical Kinetics, Harper & Row, New York, 1987, 4-6.
 
[28]  The symbol “” stands for “conditional” or “implication” arrow, and means “if… then …”. Given two propositions p and q, means “if p, then q”.
 
[29]  The symbol “” stands for “biconditional” or “equivalence” arrow. The expression “” means “p if and only if q”, that is to say the following implications hold: and .
 
[30]  Notice that eqs 32 and 33 have the following notation according to “stoichiometric amount of substance” definition: (eq 32) and (eq 33).
 
[31]  Topchiev, A. V., Zavgorodnii, S. V., Paushkin, Ya. M., Boron Fluoride and Its Compounds as Catalysts in Organic Chemistry, Pergamon Press, London, 1985, 14.