Reducing Heavy Metal Waste in Potentiometric Exercises in the General Chemistry Laboratory

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 19 (2014) pp 379-383

Reducing Heavy Metal Waste in Potentiometric Exercises in the General Chemistry Laboratory

Frazier Nyasulu*, Jenna Silverman, Brandon Allman, Rebecca Barlag, Phyllis Arthasery and Lauren McMills

Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, nyasulu@ohio.edu
Received April 10, 2014. Accepted November 24, 2014.

Published: 17 December 2014

Abstract. Potentiometric laboratory exercises in general chemistry are known for producing a considerable amount of heavy metal waste. This manuscript describes strategies for reducing this waste and increasing the efficiency of operations by using miniaturized half-cells and Cl^-(aq) based verification of the Nernst equation. Standard electrode half-cells and the reference electrode Ag(s)|AgCl(s)|Cl^-(aq,3.0 M) are constructed in autopipettor tips. The standard half-cells are: Ag(s)|Ag⁺(aq), Cu(s)|Cu²⁺(aq), Pb(s)|Pb²⁺(aq), Zn(s)|Zn²⁺(aq) and Ag(s)|AgCl(s)|Cl^-(aq). The inclusion of the Ag(s)|AgCl(s)|Cl^-(aq) standard half-cell allows the determination of K_sp (AgCl(s)) from one cell measurement and from a combination of two cells. The cell used to investigate the effect of concentration on the cell potential is Ag(s)|AgCl(s)|Cl^-(aq,3.0 M)||Cl^-(aq, α M)|AgCl(s)|Ag(s). These strategies have reduced heavy metal waste twenty-fold.

Key Words: Laboratories and Demonstrations; general chemistry; potentiometry; standard electrode potentials; Nernst equation

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

Article in PDF format (194 KB) HTML format

Supporting Materials:

There are two supporting material files; The instructor information file (s00897142596asm1.pdf), which consists of helpful information for the instructor and the information to be provided to the students and the Excel spreadsheet template (s00897142596asm2.xls), which students use to perform the calculations (366 KB).