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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 28 (2023) pp 44-47

A Simple Pressure-Based Method for the Determination of Henry’s Law Constant of CO₂in Water by Addition ofa Known Mass of CO₂(s)

Frazier Nyasulu*, Rebecca Barlag, Lauren McMills, Phyllis Arthasery, Ali H. Aldhumani and Javad Shokraiyan

Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA, nyasulu@ohio.edu
Received March 29, 2021. Accepted November 19, 2022.

Published: 24 March 2023

Abstract. The Henry’s law constant (k) is determined by adding a known mass of CO₂(s) to a known volume of water in a Schlenk flask and measuring the total gas pressure. The partial pressure of CO₂(g) is equal to the measured pressure minus the atmospheric pressure, an application of Dalton’s law. Having determined the partial pressure of CO₂(g), the moles of CO₂(g) are calculated using the ideal gas law. With moles of CO₂(g) known, the moles of CO₂(aq) are calculated and used to determine the concentration of CO₂(aq). From these, the Henry’s law constant is calculated. This is a simple and straightforward method to determine the Henry’s law constant of CO₂in water. Students report k values of 0.0318 ± 0.004 mol/(L.atm) (N = 20), which compares favorably with literature values. In order to increase the pedagogical value of this laboratory exercise, the pressure that is expected for a given set of experimental values (mass of CO₂(s), volume of Schlenk flask, volume of water, temperature, atmospheric pressure, Henry’s law constant) is predicted prior to experimentation. The mathematical manipulation that is required is well within the reach and understanding of general chemistry students.

Key Words: Laboratories and Demonstrations; high school/introductory chemistry; first-year undergraduate/general; laboratory instruction; collaborative/cooperative learning; hands-on learning/manipulatives; equilibrium; solutions/solvents; physical properties; gas

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

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