Buffers in Household Products

Product Details

Many household products contain buffering chemicals, such as citric acid, sodium carbonate, sodium benzoate and phosphates or phosphoric acid to safeguard their activity. Students discover the wide range of buffering action using this advanced inquiry lab activity.

The lab begins with an introductory activity to identify the buffering regions in the neutralization of a polyprotic weak acid. The results provide a model for guided-inquiry design of a procedure to determine the buffering agents in eight different household products, including foods and beverages and over-the-counter drugs. Procedures may include creating titration curves, calculating pK_a values and analyzing the buffer capacity and composition. Students may recommend additional consumer products for further inquiry study.

Complete for 24 students working in pairs.

2024 CED Alignment:  

Unit 8 - Properties of Buffers  

Topic 8.8 - Properties of Buffers 

Topic 8.10 - Buffer Capacity 

Description of the Lab  

Students test the pH stability of household products and lab-prepared buffer solutions by adding acid and base. They compare how buffers resist pH changes, calculate buffer capacity, and relate their findings to the concentrations of conjugate acid-base pairs. This lab gives students real context for equilibrium thinking and pH control. 

Learning Objectives 

• LO 8.8.A – Explain the relationship between the ability of a buffer to stabilize pH and the reactions that occur when an acid or a base is added to the buffered solution. 

• LO 8.10.A – Explain the relationship between the buffer capacity of a solution and the relative concentrations of the conjugate acid and conjugate base components of the solution. 

Skills Students Will Learn 

• 1.B – Describe the components of and quantitative information from models and representations that illustrate both particulate-level and macroscopic-level properties. 
  In this lab: Students represent how conjugate acid-base species interact with added H⁺ or OH⁻. 

• 5.F – Calculate, estimate, or predict an unknown quantity from known quantities by selecting and following a logical computational pathway and attending to precision (e.g., performing dimensional analysis and attending to significant figures). 
  In this lab: Students calculate initial and final pH values and interpret them in terms of buffer strength. 

• 6.F – Explain the connection between experimental results and chemical concepts, processes, or theories. 
  In this lab: Students relate differences in pH response to chemical composition and acid-base equilibrium.