Conductivity Sensor Determination of van’t Hoff Factor: A General Chemistry Laboratory Exercise

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 16 (2011) pp 85-88

Conductivity Sensor Determination of van’t Hoff Factor: A General Chemistry Laboratory Exercise

Frazier Nyasulu*, Phyllis Arthasery, and Rebecca Barlag

Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, nyasulu@ohio.edu
Received July 17, 2010. Accepted September 23, 2010.

Published: 18 March 2011

Abstract. This laboratory exercise describes conductivity measurements of solutions in the concentration range of 0.0010 M to 0.010 M using a datalogger and a conductivity sensor. These conductivities are used to determine the van’t Hoff factor, i, for NaCl(aq), Na₂SO₄(aq) and MgSO₄(aq). Considering the fact that theoretical and experimental i differ because of ion pairing, it is concluded that (a) ion pairing increases with concentration, (b) ion pairing is particularly significant when ion charge magnitudes are greater than one.

Key Words: Laboratories and Demonstrations; general chemistry; laboratory instruction; solutions; conductivity; electrochemistry

(*) Corresponding author. (E-mail: nyasulu@ohio.edu)

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Supporting Materials:

Two supporting files are available. A laboratory handout and Excel spreadsheet in a compressed zip file (443 KB).