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ERIC Number: EJ936775
Record Type: Journal
Publication Date: 2011-May
Pages: 3
Abstractor: As Provided
Reference Count: 9
ISSN: ISSN-0021-9584
Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods
Barlag, Rebecca; Nyasulu, Frazier
Journal of Chemical Education, v88 n5 p643-645 May 2011
The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such that the total mass is between 12 and 15 g. The density of the prepared solution is determined using a 1.00 mL autopipettor, and its absorbance measured. From these measurements, the water of hydration is calculated. The procedure conserves materials, produces little waste, and takes [approximately]15 min per sample; therefore, students are able to analyze the four hydrates in one lab period. The compounds are cupric sulfate pentahydrate, cupric nitrate hemi(pentahydrate), cupric chloride dihydrate, and cupric sulfate (anhydrous). Students also analyze one of these cupric hydrates by heating. The heating approach uses more material and takes longer, but the results from the two approaches are comparable. (Contains 3 tables.)
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A