Activity Template
Subject Area(s) Chemistry
Associated Unit
Acids and Bases
Associated Lesson
Activity Title
Which Base Is Best?
Header
Grade Level - (10-12)
Activity Dependency None
Time Required 2-3 class periods (90-120 minutes)
Group Size 2-4
Expendable Cost per Group US$_0__
Summary
The lab will take several class periods. One period will be devoted to the neutralization of
the acid. During a later class period, students will evaporate the liquid from the neutral
solution they have prepared in order to calculate percent yield.
Engineering Connection
Chemical and Environmental Engineers are routinely involved in environmental decisions
such as assessing different chemicals’ effects on the surrounding environment. Engineers in
general are also heavily involved in finding areas where cost-reduction can be obtained. One
example is determining the most cost-effective way of disposing of a chemical. Chemical
engineers also use the properties of chemicals involved in reactions to design more useful
forms of the chemicals.
Engineering Category
(1) relates science concept to engineering
Keywords
Acid, Base, Neutral, pH, Titration, Mole, Neutralization
Educational Standards
 Alabama Course of Study: Grade 9-12, Chemistry Standard 4.3: Describe acids and
bases in terms of strength, concentration, pH, and neutralization reactions.
 Alabama Course Of Study: Grade 9-12, Chemistry Standard 6: Solve stoichiometry
problems involving relationships among the number of particles, moles, and masses of
reactants and products in a chemical reaction.
 State Math: Alabama Course of Study: Grade 9-12, Algebra Standard 1: Simplify
numerical expressions using properties of real numbers and order of operations, including
those involving square roots, radical form, or decimal approximations.
 State Math: Alabama Course of Study: Grade 9-12, Algebra Standard 15: Estimate
probabilities given data in a list or graphs.
Pre-Requisite Knowledge
Students should be familiar with

balancing chemical equations and solving stoichiometric problems

basic definitions of acids/ bases

proportion calculations

lab techniques and safety precautions
Learning Objectives
After this activity, students should be able to:



Solve stoichiometric problems in mass-mass relationships.
Calculate percent yield using experimental data.
Relate experimental results to cost effectiveness in a real world application.
Materials List
Each group needs:
Day 1: Neutralization
Analytical balance
SpatulaAssigned Base
50 mL beaker
Graduated cylinder
Buret
Weigh boat
Buret Clamp GLX and adaptor
2-250 mL Beakers
Funnel
1 M HCl
Distilled Water
pH sensor
Day 2: Evaporation
Neutralized solution from Day 1
Analytical balance
Spatula
Gauze Square
Tongs
Evaporating dish
Hot mitt
Hotplate
Watch glass
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To share with the entire class:

3-5 analytical balances
Introduction / Motivation
Identifying the Problem:
One of the byproducts of The Chemical Company’s Production Line A is hydrochloric acid.
Environmental regulations require neutralization of this acid before disposal. Your
department has been assigned the task of determining the most cost effective method of
neutralization.
Design Constraints:
In addition, it would be beneficial if the product of this neutralization reaction may also be
profitable for the company, therefore you need to develop a method which results in a high
percent yield. Your group will be assigned one of the following bases to test in neutralizing
the acid.
Base A: Sodium hydroxide: Cost-$57.17/1kg
Base B: Sodium carbonate: Cost-$13.11/1kg
Base C: Sodium bicarbonate: Cost-$18.92/1kg
Vocabulary / Definitions
Word
Definition
3
that combine during chemical reactions
Procedure
Day One- Prelab:
1. Complete the Webquest on Acids and Bases so that you have enough background
knowledge to continue.
2. Predict which of the bases presented in the problem will be the most cost effective for
your company to use in neutralizing the acid. Below are the pH values for various
common acids and bases. Use these facts to support your prediction.
Chemical
Molarity
pH
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Day Two- Neutralization of Acid:
In this reaction you will measure the mass of solid reactant assigned and that of the solid
product. You will also measure the volume of hydrochloric acid neutralized. You will then
determine the actual, theoretical, and percent yields of the reaction and share with your
department to determine which of these bases is most cost effective.
Safety:
Wear safety goggles and aprons. If any acid should spill on you, immediately flush the
area with water and notify the teacher. Be careful handling the glassware during heating.
Objectives:
After completing this experiment the student will be able to:
a.
Set up a GLX pH meter for titration.
b.
Titrate an acid with a strong base to determine the volume needed for
neutralization.
Materials:
Analytical balance
Spatula
Assigned Base
Graduated cylinder
Buret
Weigh boat
Buret Clamp GLX and adaptor
2-250 mL Beakers
1 M HCl
Funnel
50 mL beaker
Distilled Water
pH sensor
Testing and Evaluating:
Procedure:
1. Place a weigh boat on the balance. Zero the balance with the weigh boat in place.
2. Add approximately 0.50 grams of your assigned base to the weigh boat. Record this mass in
the DATA TABLE.
3. Remove the weigh boat from the balance and place the solid in a beaker.
4. Add 10 mL of distilled water and stir to dissolve the base.
5. Set up the ring stand and buret as directed by your instructor.
6. Plug in GLX with the power adaptor. Attach the pH sensor in Channel 1. Do not remove the
buffer solution yet.
7. Turn on the GLX using the
.
8. Obtain a beaker for wash water and a wash bottle containing distilled (or deionized) water.
9. Always rinse the electrode with distilled water into a beaker labeled as "Waste Beaker".
10. Fill the buret past the 0.00 mL mark with the 1M HCl standard solution and deliver the
excess into a waste beaker while ridding the buret tip of air bubbles. Adjust the HCl
standard solution to the 0.00 mark of the buret.
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11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
Remove the buffer solution container. (Place it in a 50 mL beaker so that it will not
spill.) Keep the ‘O’ ring and buffer lid on the electrode. Slide them up on the electrode so
that they will not be in the way during titration.
Rinse the buffer off of the electrode with distilled water into the waste container and
blot. Immerse the electrode in the base solution.
On the GLX pH value should be visible. If you do not have a pH reading, use arrow keys
to move right to highlight the Meter box.
Begin adding the HCl slowly, about ½ mL at a time. Stop frequently intervals to swirl
the solution and observe the pH.
When the pH reaches 8.0 begin adding dropwise.
When the pH reaches 7.0 or slightly below and stays there for about 1 minute, your
solution is neutral.
Record the total volume of acid used in the data table.
Write your group name on a vial. Pour your neutral solution into the container and set
aside in a designated area for further experimentation.
Rinse off the pH electrode and replace it in the buffer solution.
Wash the buret completely (including the tip) with deionized water at least three times.
Leave the buret open and inverted in the buret clamp so that it will drain optimally.
Wash all used glassware and rinse with deionized water.
Wash your hands well before leaving the lab.
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Day Three- Evaporation to Determine Salt Yield:
Safety:
Wear safety goggles and aprons. If any acid should spill on you, immediately flush the
area with water and notify the teacher. Be careful handling the glassware during
heating.
Objectives: After completing this experiment the student will be able to:
a. investigate mass and mole relationships in reactants and products of a reaction.
Materials:
Neutralized solution from Day 2
Analytical balance
Spatula
Gauze Square
Tongs
Evaporating dish
Hot mitt
Hotplate
Watch glass
1. Weigh the evaporating dish and watch glass together and record in Data Table 2.
2. Pour one half of your neutralized solution into the evaporating dish.
3. Reweigh the evaporating dish and watch glass with the neutral solution and record on Data
Table 2.
4. Place the evaporating dish on a hotplate with the watch glass on top. Turn the hotplate on 5.
Heat the reaction mixture until a dry solid remains. If it starts to boil, turn the hotplate down
to 3 or 4. Make sure no water droplets remain on the underside of the watch glass.
5. Allow the evaporating dish and watch glass to cool for about 15 minutes. Determine the
mass of the dish, residue, and the watch glass and record in the DATA TABLE.
6. If time permits, reheat the evaporating dish and contents for two minutes more to be sure all
the liquid has been driven off. Cool and re-weigh.
7. Rinse the residue down the sink. Clean up your lab area and wash your hands before leaving
the lab.
8. Complete calculations and questions.
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STUDENT WORKSHEET: Chemical Reactions and Stoichiometry Module
Student Name:___________________
DATA TABLE 1:
Used:______________________
Base
Mass of Reactant, Base
g
1. Write a correctly balanced equation for your neutralization reaction.
Extension/Quality Control:
1. Based on the volume of acid neutralized and the cost of your assigned base, calculate the
cost of neutralizing 10 L of 1 M HCl using this base. SHOW ALL WORK BELOW.
Cost of Neutralizing 10 L of 1 M HCl =
A. Cost of Base Used = (Mass of Reactant Base)( 1 Kg )(Cost of base)
1
1000g
1 Kg
B. Cost Per Volume = Cost of Base Used
Volume of acid neutralized
C. Cost Per 10L HCl = (Cost Per Volume)(10,000 mL)
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DATA TABLE 2:
Mass of dish, glass, and neutral solution
g
Calculations: SHOW ALL WORK.
1. Calculate the mass of reactant (base) used.
2. Calculate the mass of product (NaCl). REMEMBER to multiply the mass of residue by
two since you only evaporated one half of the original neutralized solution
3. Calculate the theoretical yield of NaCl based on the amount of base used and the
balanced equation.
4. Calculate the percentage yield of the NaCl.
CALCULATIONS TABLE
1. Mass of Reactant, Base
g
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Extension/Quality Control:
2. What are some plausible reasons why your percent yield is less than 100%? What are
some plausible reasons why your percent yield is more than 100%?
3. Compare your final cost and percent yield results with the other groups to determine the
most cost effective method of acid neutralization for the class as a whole.
BASE A
BASE B
BASE C
Image Figure 1: GLX with pH sensor SourceAlabama Science In Motion
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Attachments
 Webquest


Teacher Notes
Safety Issues
Wear safety goggles and aprons. If any acid should spill on you, immediately flush the area
with water and notify the teacher. Be careful handling the glassware during heating.
Troubleshooting Tips
 Remind students to use only half of neutralized
Investigating Questions
Assessment
Pre-Activity Assessment
Title: _Acid-Base Webquest__
Activity Embedded Assessment
Title: _Lab Report with Calculations__
Post-Activity Assessment
Title: ___
Activity Extensions
Day One Extension:
Extension/Quality Control:
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1. Based on the volume of acid neutralized and the cost of your assigned base, calculate the
cost of neutralizing 10 L of 1 M HCl using this base. SHOW ALL WORK BELOW.
Day Two Extension:
Extension/Quality Control:
1. What are some plausible reasons why your percent yield is less than 100%? What are
some plausible reasons why your percent yield is more than 100%?
2. Compare your final cost and percent yield results with the other groups to determine the
most cost effective method of acid neutralization for the class as a whole.
BASE A
BASE B
BASE C

Activity Scaling
For lower grades, __This activity is not appropriate for grades lower than high school
chemistry.

For upper grades, ___This activity is designed for an advanced chemistry class.
Additional Multimedia Support
NONE
References
This lab was adapted from several labs used by Alabama Science In Motion(ASIM). These labs
are Mass/Mole Relationships in a Chemical Reaction and Strong Acid/Strong Base
Macrotitration. The website for ASIM is https://fp.auburn.edu/asim
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Other
Redirect URL
Owner
Contributors Beth Sherrill, Karen Garrison, Felecia Briggins, Brett Gunter
Copyright
Version: January 2009
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