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ERIC Number: EJ820742
Record Type: Journal
Publication Date: 2007-Mar
Pages: 3
Abstractor: As Provided
Reference Count: 9
ISBN: N/A
ISSN: ISSN-0021-9584
Flame Emission Spectrometry in General Chemistry Labs: Solubility Product (K[subscript sp]) of Potassium Hydrogen Phthalate
Nyasulu, Frazier W.; Cusworth, William, III; Lindquist, David; Mackin, John
Journal of Chemical Education, v84 n3 p456-458 Mar 2007
In this general chemistry laboratory, flame emission spectrometry is used to determine the potassium ion concentration in saturated solutions of potassium hydrogen phthalate (KHP) in the 0-65 [degree]C temperature range. From these data the solubility products (K[subscript sp]), the Gibbs free energies of solution ([Delta][subscript soln]G[degree]), the standard enthalpy of solution ([Delta][subscript soln]H[degree]), and the standard entropy of solution ([Delta][subscript soln]S[degree]) are calculated. Students also determine K[subscript sp] in 0.50 M KCl at room temperature wherein the K[superscript +] concentration is determined by flame emission and HP[superscript -] concentration is determined via titrating with NaOH. In determining both the K[superscript +] and HP[superscript -] concentrations in a saturated solution of KHP in 0.50 M KCl, students verify that K[subscript sp] is a constant by showing that the same numerical values are obtained, with and without KCl. This experiment also addresses one of the serious problems we and many others have noticed; students do not know how to prepare solutions accurately, especially dilute solutions. We therefore require our students to prepare the K[superscript +] calibration standards from KHP(s). As an additional exercise, students determine the concentration of potassium in Gatorade. (Contains 2 tables.)
Division of Chemical Education of the American Chemical Society. Subscription Department, P.O. Box 1267, Bellmawr, NJ 08099-1267. Tel: 800-691-9846; Tel: 856-931-5825; Fax: 856-931-4115; e-mail: jchemed@egpp.com; Web site: http://www.jce.divched.org
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A