Module 7 Intro

1.16. Page 2

Module 7—Chemical Analysis

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In Lesson 2 you performed a titration of an acid using a base. During that process, many changes occurred within the chemical system, some of which you were able to see and others you were not. In this lesson you will apply your knowledge of stoichiometry to explain the changes that occur within a chemical system during a titration. To begin, read the first paragraph of “8.5 Acid-Base Titration Curves and Indicators” on page 333 of your textbook.

 

Titration Curves

 

A titration curve is a graph of the change in pH of the system being studied as a standardized solution is added. Recall that a titration involves adding small amounts of titrant to the test solution. What if you had the chance to assess the changes in the system after each addition of titrant—what would you want to measure? What would the pattern of the change look like?

 

Try This

 

Drawing a Titration Curve

 

In this activity you will draw a titration curve using the data you generate in a virtual titration experiment. Combining acids and bases causes neutralization and, therefore, a change in the pH of the solution. To monitor the progress of your titration, you will record pH throughout the titration.

 

Purpose

You will draw a titration curve.

 

Problem

What is the shape of a titration curve?

 

Procedure

 

Step 1: Construct a data table like the following.

 

Volume of Titrant Added	pH of Test Solution	Indicator Colour

 

Title the data table “Titration of HCl(aq) with 1.0-mol/L NaOH(aq).”

 

Step 2: Open the “Titration of an Acid” virtual lab.

 

 

Step 3: Read the instructions and complete Procedures 1 and 2 as described in the instructions. As you proceed through the titration, record your observations in the appropriate places in your data table.

 

Step 4: Use graph paper or a spreadsheet program to construct a graph of pH (vertical axis) versus Volume of 1.0-mol/L NaOH(aq) Added (horizontal axis).

 

Step 5: On the graph, label where the colour change of the phenolphthalein indicator occurred.

 

Step 6: Add a suitable title, and ensure the features of your graph are appropriately labelled. Save your work in your course folder.

 

Module 7: Lesson 3 Assignment

 

Copy your titration curve from the Try This activity above into the space provided for question 1 in the Module 7: Lesson 3 Assignment that you saved to your course folder at the beginning of the lesson. Save your Module 7: Lesson 3 Assignment to your course folder.