Vernier Software & Technology

# Sour Chemistry - The Exponential pH Change

## Introduction

Chemists quantify the acidity or alkalinity of a solution by measuring its pH on a scale ranging from 0 to 14. A neutral substance has a pH of 7. A pH lower than 7 suggests an acidic solution, while a pH higher than 7 indicates that a solution is basic.

Different pH levels must be maintained throughout the body in order for a person to remain healthy. Excessively high or low pH levels often result in discomfort or irritation. For example, common indigestion or upset stomach usually indicates the presence of excessive amounts of stomach acids. This condition can sometimes be alleviated by taking an antacid tablet, or by drinking a solution such as Alka-SeltzerĀ® and water, designed to neutralize these acids and raise the pH level in the stomach.

In this activity, the conditions found in an acid stomach will be simulated using a solution of lemon juice and water. The effectiveness of an antacid remedy will be tested by monitoring the pH of the solution after an effervescent antacid tablet has been added to it. The resulting data will be modeled using a modified exponential function.

## Objectives

• Record pH versus time data as an antacid tablet neutralizes the acid in lemon juice.
• Model the pH data with a modified exponential function.

## Sensors and Equipment

This activity features the following Vernier sensors and equipment.

You may also need an interface and software for data collection. What do I need for data collection?

## Real-World Math with Vernier

See other experiments from the lab book.

 1 Walk the Line - Straight Line Distance Graphs 2 Making Cents of Math: Linear Relationship between Weight and Quantity 3 Pool Plunge - Linear Relationship between Water Depth and Pressure 4 Funnel Volumes - Volume and Weight 5 Keep It Bottled Up - Rates of Pressure Increase 6 Mix It Up - Mixing Liquids of Different Temperatures 7 Spring Thing - Newton's Second Law 8 Stretch It to the Limit - The Linear Force Relation for a Rubber Band 9 What Goes Up - Position and Time for a Cart on a Ramp 10 That's the Way the Ball Bounces - Height and Time for a Bouncing Ball 11 Walk This Way - Definition of Rate 12 Velocity Test - Interpreting Graphs 13 From Here to There - Applications of the Distance Formula 14 Under Pressure - The Inverse Relationship between Pressure and Volume 15 Light at A Distance - Distance and Intensity 16 Chill Out: How Hot Objects Cool 17 Charging Up, Charging Down - Charging a Capacitor 18 Bounce Back - The Pattern of Rebound Heights 19 Sour Chemistry - The Exponential pH Change 20 Swinging Ellipses - Plotting an Ellipse 21 Lights Out! - Periodic Phenomena 22 Tic, Toc: Pendulum Motion 23 Stay Tuned: Sound Waveform Models 24 Up And Down: Damped Harmonic Motion 25 How Tall? Describing Data with Statistical Plots 26 And Now, the Weather - Describing Data with Statistics 27 Meet You at the Intersection: Solving a System of Linear Equations 28 Titration Curves: An Application of the Logistic Function 29 Clock Design: Period and Length of a Simple Pendulum 30 Graph It in Pieces: Piecewise Defined Functions 31 Stepping to the Greatest Integer: The Greatest Integer Function 32 Crawling Around: Parametric Plots

### Activity 19 from Real-World Math with Vernier Lab Book

#### Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.