The Method of Continuous Variation: A Laboratory Investigation of the Formula of a Precipitate

The method of continuous variation is applied to the reaction between barium chloride and diammonium hydrogen phosphate in neutral, acidic, and basic conditions. Depending on the medium, barium dihydrogen phosphate, barium hydrogen phosphate, or barium phosphate is precipitated. The precipitates are...

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Bibliographic Details
Published inJournal of chemical education Vol. 90; no. 7; pp. 937 - 940
Main Authors Furlong, William R, Rubinski, Miles A, Indralingam, Ramee
Format Journal Article
LanguageEnglish
Published Easton American Chemical Society and Division of Chemical Education, Inc 09.07.2013
American Chemical Society
Subjects
Analytical chemistry
Barium
Barium chloride
Chemical reactions
Deduction
Hydrogen ion concentration
Logic
Phosphates
Precipitates
Reagents
Science education
Students
Hands-On Learning/Manipulatives
Quantitative Analysis
First-Year Undergraduate
Stoichiometry
Analytical Chemistry
Laboratory Instruction
Physical Chemistry
Second-Year Undergraduate/General
Gravimetric Analysis
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Summary:The method of continuous variation is applied to the reaction between barium chloride and diammonium hydrogen phosphate in neutral, acidic, and basic conditions. Depending on the medium, barium dihydrogen phosphate, barium hydrogen phosphate, or barium phosphate is precipitated. The precipitates are washed, dried, and weighed. Construction of a continuous variation plot for each condition leads to the deduction of the molecular formula of the phosphate precipitated. This experiment demonstrates the concept of stoichiometric relationships between ions in the formation of compounds and serves to give students practice in calculations involving limiting reagents.
ISSN:0021-9584
1938-1328
DOI:10.1021/ed3004337