The Equilibrium Constant

Abstract

This activity addresses the confusion chem students encounter when trying to memorize “rules” for writing an equilibrium constant expression from a balanced chemical equation. There are so many little details and exceptions that students are overwhelmed rather than confident as they try to master the concept of writing K_eq expressions.

This activity presents three Models that build in difficulty level. In  Model 1, students explore and describe patterns between six balanced chemical equations and their K_eq expressions as they learn to translate “+” symbols and coefficients in the chemical reaction to dot symbols and exponents in the K_eq expression. In Model 2, students explore six additional balanced chemical equations and their K_eq expressions as they distinguish (s), (l), (g), and (aq) phases of chemicals and discover how to represent each phase in a K_eq expression. The optional Extension Questions introduce the quantification of K_eq expressions and the meaning of K_eq values less than, equal to, or greater than 1.

Level: High School, Undergraduate first year

Setting: Classroom

Activity Type: Learning cycle – concept development)

Discipline: Chemistry

Course: HS Honors Chemistry, College General Chemistry

Keywords: Equilibrium, Equilibrium Constant Expressions