pH
Volume of Titrant
Acid-Base Titration
O12-10732 r1.04
Acid-Base Titration
Introduction
Journals and Snapshots
The Snapshot button is used to capture the
screen.
The Journal is where snapshots are stored
and viewed.
The Share button is used to export
or print your journal to turn in your
work.
Each page of this lab that
contains the symbol
should be inserted into your
journal. After completing a
lab page with the snapshot
symbol, tap
(in the upper
right hand corner) to insert
the page into your journal.
Note: You may want to take a
snapshot of the first page of
this lab as a cover page for
your Journal.
Acid-Base Titration
Lab Challenge
Many foods and household products contain acids and bases. Knowing if a sample is
acidic or basic is only part of the question. How do you determine the actual
amount of acid or base dissolved in a solution?
Acid-Base Titration
Background
• Titration is a common quantitative laboratory
method used to determine the concentration of a
reactant.
• A reagent of known concentration, called the
titrant, is used to react with a measured volume
of another reactant, called the analyte.
• The point at which the number of moles of the
titrant and the analyte are equal is called the
equivalence point. On a titration curve, the
equivalence point is the point where the slope is
the steepest.
Titrant
Analyte
Equivalence
point
Acid-Base Titration
...Background
• When a basic solution is added to an acidic solution of unknown concentration,
hydroxide ions (OH-) from the basic solution react with hydronium ions (H3O+)
from the acidic solution to form neutral water and a salt. The type of salt
formed depends on the acid and base used.
• This is called a neutralization reaction.
+
Acidic solution

Basic solution
Neutral solution
Acid-Base Titration
Self-Check
1. Titrations are used to determine the
_____________ of a reactant.
a) density
b) pH
c) mass
d) concentration
This image is a reminder that
you need to tap
to take a
snapshot of this page after
you have entered your
response.
Acid-Base Titration
Safety
• Follow all common laboratory safety procedures
• Sodium hydroxide, hydrochloric acid, and acetic
acid are corrosive irritants. Avoid contact with the
eyes and wash hands after handling.
• When mixing acids with water, always add the
acid to the water, not the other way around, as
the solution can get hot enough to boil.
• Be sure that all acids and bases are neutralized
before being disposed of down the drain.
BE SAFE
Always wash hands
to remove residue
before leaving
Acid-Base Titration
Materials and Equipment
Collect all of these materials before beginning the lab.
•
•
•
•
•
•
•
•
•
Drop counter
pH sensor
Magnetic stirrer
Micro stir bar
Beakers (2), 50-mL
Buffer solution pH 4, 25 mL
Buffer solution pH 10, 25 mL
Funnel
Graduated cylinder, 100-mL
Acid-Base Titration
...Materials and Equipment
Also collect these additional materials before beginning.
•
•
•
•
•
•
•
Buret, 50-mL
Buret clamp
Ring stand
Right-angle clamp
Beakers (2), 250-mL
Transfer pipet
Volumetric pipet or graduated
cylinder, 10-mL
• Wash bottle filled with distilled
(deionized) water
Acid-Base Titration
...Materials and Equipment
Also collect these additional materials before beginning.
• Waste container
• deionized (distilled water), 200 mL
• Standardized sodium hydroxide solution, 100 mL
• Hydrochloric acid solution, 10 mL
• Acetic acid solution, 10 mL
waste
waste
Distilled
Water
Acid-Base Titration
Sequencing Challenge
A. Setup the titration
equipment and
calibrate the pH
sensor.
B. Measure and
record the starting
volumes of NaOH
and HCl. Start
collecting data and
then release the
titrant.
C. Thoroughly clean
the equipment and
then repeat the
procedure using
acetic acid.
D. When the pH is
12, close the
stopcock and then
stop collecting data.
Record the final
volume of NaOH.
The steps to the left are part of
the procedure for this lab
activity. They are not in the
right order. Determine the
correct sequence of the steps,
then take a snapshot of this
page.
Acid-Base Titration
Setup: HCl Titration
1. Connect the pH sensor to the data collection system.
2. Calibrate the pH sensor:
a. Pour approximately 25 mL of the pH 4 buffer
solution in a 50-mL beaker.
b. Pour approximately 25 mL of the pH 10 buffer
solution in a second 50-mL beaker.
c. Remove the pH sensor from its electrode storage
bottle and rinse it with distilled water to
thoroughly clean the sensor.
d. Read the instructions on how to calibrate the pH
sensor on the next page.
Buffer solutions and pH sensor
Acid-Base Titration
To Calibrate the pH Sensor:
Note: During the calibration process you
will not be able to return to this page.
1. Open the Calibrate Sensor screens:
a. Tap
b. Tap CALIBRATE SENSOR
2. Ensure that the correct
measurements are selected:
a. Sensor: (name of sensor)
Measurement: pH
Calibration Type: 2 point
b. Tap NEXT
3.
Calibration Point 1:
a. Place the pH probe in a pH 4 buffer
solution.
b. Enter 4.0 as the pH in the Standard
Value box under Calibration Point 1.
c. Tap Read From Sensor under
Calibration Point 1.
d. Rinse the pH probe thoroughly using
distilled water.
4. Calibration Point 2:
a. Repeat the process used in calibration point
1 using a pH 10 buffer solution.
b. Tap OK to exit the calibration screen and
then tap OK again to return to the lab.
Acid-Base Titration
Setup: HCl Titration
3. Connect the drop counter to the data collection
system.
4. Assemble the titration apparatus.
Buret clamp
Ring stand
Buret
pH sensor
Right-angle clamp
Drop counter
Beaker, 250-mL
Micro stir bar
Magnetic stirrer
Q1: Using the terms
accuracy and
precision, explain why
it is necessary to
calibrate the pH
sensor.
Acid-Base Titration
Setup: HCl Titration
5. Use a transfer pipet to rinse the inside of the buret with
several milliliters of the standardized sodium hydroxide
(NaOH) solution.
6. Drain the NaOH from the buret into the waste container.
7. Repeat this process two more times.
8. Make sure the stopcock on the buret is in the "off"
position and then use a funnel to fill the buret with
~50 mL of the standardized NaOH solution (titrant).
Off
position
On
position
Q2: Why is it necessary to
rinse the buret with
standardized NaOH
solution?
Acid-Base Titration
Setup: HCl Titration
9. Practice adjusting the stopcock on the buret so
that the titrant goes through the drop counter in
distinguishable drops that fall at about 2 to 3 drops
per second.
Note: It is important that you have good control of adjusting the
stopcock. If you accidently open the stopcock too far and the
NaOH flows out (as opposed to drops out), then you will have to
start over.
10.Close the stopcock and then remove the waste
container.
Q3: Why is it be necessary
to start your titration
over again if you
accidently allow the
titrant to flow out of
the stopcock instead of
drop?
Acid-Base Titration
Setup: HCl Titration
11. Read the initial volume of the titrant in the buret
to 0.01 mL.
12. Using the 100-mL graduated cylinder measure
100 mL of distilled water and add it to a clean
250-mL beaker.
13. Using the 10-mL graduated cylinder or
volumetric pipet measure 10.0 mL of
hydrochloric acid (HCl) and add it to the
100 mL of distilled water. Record the exact
volume of HCl added in the text box on the next
page.
Caution: Always add acid to water.
Q4:Record the initial
volume of NaOH and
the concentration of
the standardized NaOH
solution in the text box
below.
Acid-Base Titration
Setup: HCl Titration
14.Add the pH sensor, micro stir bar, and 250-mL
beaker containing the acidic solution to the
titration apparatus.
15.Turn on the magnetic stirrer and begin stirring at
a slow to medium speed.
Note: Make sure the bulb of the
pH sensor is fully submerged.
Q5: Record the volume of
HCl added to the
beaker in the text box
below.
Acid-Base Titration
Collect Data:
1. Tap
to start collecting
data.
2. Carefully open the
stopcock on the buret so
that 2 to 3 drops per
second are released.
3. Continue to collect data
until the pH of the solution
is 12.
Continue to the next page.
Acid-Base Titration
Q6: Why is it necessary to stir Q7:What substances are
the solution during a
being formed in the
titration?
beaker?
Acid-Base Titration
Collect Data:
4. When the pH of the
solution is 12 close the
stopcock.
Continue to the next page.
Acid-Base Titration
Collect Data:
5. Tap
to stop data
collection.
6. Record the final volume of
NaOH in the buret.
Acid-Base Titration
Data Analysis: HCl
1. Determine the total volume of NaOH used in the
titration by following steps a-c below.
Volume NaOH = Final Volume NaOH - Initial Volume of NaOH
Note: Initial and final volumes of NaOH were recorded earlier
in the journal. Refer to the journal to get these numbers.*
a. Enter the final volume of NaOH in the text box on
the right.
b. Record the initial volume of NaOH in the text box on
the right
c. Subtract the initial volume of NaOH from the final
volume of NaOH and record the total volume in the
text box on the right.
* To View a Page in the Journal:
1. Tap
to open the Journal
screen.
2. Tap
or
to scroll through
the thumbnail size pages of
the journal.
3. Tap the thumbnail image of
the page to view it.
Acid-Base Titration
Data Analysis: HCl
2. Create a calculation to convert drop count to
volume (mL). *
CalcVolume1 = [drop count]*(volume of titrant/final drop count)
Note:
[drop count]
=
volume of titrant =
final drop count =
collected data
total volume of NaOH used
(it is in your journal)
the total number of drops added
(it is displayed on the right)
*To Create a Calculation:
1. Tap
to open the
Experiment Tools screen.
2. Tap CALCULATED DATA to
open the calculator.
3. Enter the calculation in the
space provided.
4. Tap Measurements to insert
collected data into the
calculation.
Acid-Base Titration
3. Change the x-axis to display
CalcVolume1 of NaOH.
•Tap
then
to open the
Graph Properties screen.
•Tap the Measurement box for the
x-axis and tap CalcVolume1. Then
tap OK. Tap
to scale the axes.
4. Display the volume of
NaOH at the equivalence
point. The equivalence point
is the point on the curve
with the greatest slope and
is found using the slope tool.
•Tap
then
to see the slope.
•Tap or buttons to move to
nearby points.
•Tap
.
Acid-Base Titration
Data Analysis: HCl
5. Calculate the molar concentration of HCl. Follow the steps below:
a. Determine the number of moles of NaOH added using the volume of NaOH at the
equivalence point and the molarity of the standardized NaOH solution.
b. Convert from moles of NaOH to moles of HCl using the balanced chemical equation.
c. Use the moles of HCl and the starting volume of HCl to determine the molarity of the
acid.
Note: the values need for the calculations above can be found in your journal
.
Acid-Base Titration
Setup: Acetic Acid Titration
1. Turn off the magnetic stirrer and then remove the
beaker. Dispose of its contents according to your
teacher's instructions.
2. Place the waste container under the pH sensor and
use the wash bottle to thoroughly clean the micro
stir bar and the pH sensor.
3. Re-fill the buret so that there is ~50 mL of the
standardized NaOH solution.
4. Read the initial volume of the titrant in the buret
to 0.01 mL.
Q1: Record the initial volume
of NaOH, the
concentration of the
standardized NaOH
solution in the text box
below.
Acid-Base Titration
Setup: Acetic Acid Titration
5. Using the 100-mL graduated cylinder measure 100 mL
of distilled water and add it to a clean 250-mL beaker.
6. Using a clean 10-mL graduated cylinder or volumetric
pipet measure 10.0 mL of acetic acid and add it to the
100 mL of distilled water.
Caution: Always add acid to water.
7. Remove the waste container from the titration
apparatus and replace it with the 250-mL beaker
containing the acetic acid solution.
8. Reposition the pH sensor and then turn on the
magnetic stirrer and begin stirring at a slow to medium
speed.
Q2: Record the volume of
the acetic acid solution
that was added to the
beaker in the text box
below.
Acid-Base Titration
Collect Data: A.A.
1. Tap
to start collecting
data.
2. Carefully open the
stopcock on the buret so
that 2 to 3 drops per
second are released.
3. Continue to collect data
until the pH of the solution
is 12.
Continue to the next page.
Acid-Base Titration
Q3: What substances are
being formed in the
beaker?
HC2H3O2 + NaOH  ?
Acetic Acid = HC2H3O2
Q4: What type of reaction
is occurring?
Acid-Base Titration
Collect Data: A.A.
4. When the pH of the
solution is 12 close the
stopcock.
Continue to the next page.
Acid-Base Titration
Collect Data: A.A.
5. Tap
to stop data
collection.
6. Record the final volume of
NaOH in the buret.
Acid-Base Titration
Data Analysis: Acetic Acid
1. Determine the total volume of NaOH used in the titration.
Follow steps a-c below.
Volume NaOH = Final Volume NaOH - Initial Volume of NaOH
Note: Initial and final volumes of NaOH were recorded earlier
in the journal. Refer to the journal to get these numbers.*
a. Enter the final volume of NaOH in the text box on
the right.
b. Record the initial volume of NaOH in the text box on
the right
c. Subtract the initial volume of NaOH from the final
volume of NaOH and record the total volume in the
text box on the right.
* To View a Page in the Journal:
1. Tap
to open the Journal
screen.
2. Tap
or
to scroll through
the thumbnail size pages of
the journal.
3. Tap the thumbnail image of
the page to view it.
Acid-Base Titration
Data Analysis: Acetic Acid
2. Create a calculation to convert drop count to
volume (mL). *
CalcVolume2 = [drop count]*(volume of titrant/final drop count)
Note:
[drop count]
=
volume of titrant =
final drop count =
the collected data
total volume of NaOH used
(it is in your journal)
the total number of drops added
(it is displayed on the right)
*To Create a Calculation:
1. Tap
to open the
Experiment Tools screen.
2. Tap CALCULATED DATA to
open the calculator.
3. Enter the calculation in the
space provided.
4. Tap Measurements to insert
collected data into the
calculation.
Acid-Base Titration
3. Change the x-axis to display
CalcVolume2 of NaOH.
•Tap
then
to open the
Graph Properties screen.
•Tap the Measurement box for the
x-axis and tap CalcVolume1. Then
tap OK. Tap
to scale the axes.
4. Display the volume of
NaOH at the equivalence
point. The equivalence point
is the point on the curve
with the greatest slope and
is found using the slope tool.
•Tap
then
to see the slope.
•Tap or buttons to move to
nearby points.
•Tap
.
Acid-Base Titration
Data Analysis: Acetic Acid
5. Calculate the molar concentration of acetic acid. Follow the steps below:
a. Determine the number of moles of NaOH added using the volume of NaOH at the
equivalence point and the molarity of the standardized the NaOH solution.
b. Convert from moles of NaOH to moles of acetic acid using the balanced chemical equation.
c. Use the moles of acetic acid and the starting volume of acetic acid to determine the
molarity of the acid.
Note: the values need for the calculations above can be found in your journal
.
Acid-Base Titration
Analysis
1. What is the significance of the point on the titration curve where the slope is the
steepest?
Acid-Base Titration
Analysis
2. What trend did you notice
in the slope of the
titration curve between
the start of the titration
and the equivalence
point?
Acid-Base Titration
Analysis
3. What is the likelihood that the concentration of acid and base is exactly equal at the
experimentally determined equivalence point? Explain your reasoning.
Acid-Base Titration
Analysis
4. What difference do you
notice between the start of
the titration and the
equivalence point in the
appearance of the titration
curve for the two
different acids?
Acid-Base Titration
Analysis
5. What is the difference
between pH at the
equivalence points between
the two titration curves for
the different acids? Explain.
Acid-Base Titration
Synthesis
1. How could you determine the concentration of an unknown sodium hydroxide
solution?
Acid-Base Titration
Synthesis
2. Use the Prediction Button
to sketch the titration
curve for an acid that is
weaker than acetic acid.
*To Draw a Prediction:
1. Tap
to open the tool
palette.
2. Tap
then use your finger
to draw your prediction.
3. Tap
when finished.
4. If you make a mistake, tap
to clear your prediction.
Acid-Base Titration
Synthesis
3. Explain the difference between the strength and the concentration of an acid
solution.
Acid-Base Titration
Multiple Choice
1. For the titration of an acid with a base, the pH
will start _________ and finish ________.
Hint: the acid is the analyte in the beaker and the base is the
titrant in the buret.
a) low; low
b) high; low
c) low; high
d) high; high
Base
Acid
Acid-Base Titration
Multiple Choice
2. On a titration curve, the equivalence point is
____________________________.
a) the point with the smallest slope.
b) the point with the greatest slope.
c) the point with a slope of zero.
d) when the pH is equal to zero.
Titration Curve
Acid-Base Titration
Multiple Choice
3. An ________ in the hydronium ion concentration
in an aqueous solution causes the hydroxide ion
concentration to ________ and the pH of the
solution to _________.
a)
Increase; increase; increase
b) Decrease; decrease; decrease
c)
Increase; decrease; decrease
d) Increase; decrease; increase
Acidic solution
Acid-Base Titration
Multiple Choice
4. A reaction between an acid and a base is called
a(n) ______________.
a) pH reaction
b) titration reaction
c) s-shaped curve
d) neutralization reaction
Acid-Base Titration
Multiple Choice
5. Titrations are used to __________________.
a) determine the concentration of known solutions
b) determine the pH of known solutions
c) determine the type of molecules in a solution
d) differentiate an acid from a base
Acid-Base Titration
Congratulations!
You have completed the lab.
Please remember to follow your teacher's instructions for cleaning-up and submitting
your lab.
Acid-Base Titration
References
All images were taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons.
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SODA http://freeclipartnow.com/food/beverages/soda/soda-can.jpg.html
SALAD http://freeclipartnow.com/food/salad/salad_png-rl.jpg.html
GLASS CLEANER http://freeclipartnow.com/household/chores/cleaners/glass-cleaner.jpg.html
VINEGAR http://freeclipartnow.com/household/chores/cleaners/vinegar.jpg.html
LEMONS http://freeclipartnow.com/food/fruits/grapefruits/grapefruit-4.jpg.html
BURET http://commons.wikimedia.org/wiki/File:buret.svg
BEAKER http://www.freeclipartnow.com/science/flasks-tubes/beaker-2.jpg.html
BEAKER http://freeclipartnow.com/science/flasks-tubes/beaker.jpg.html
CORROSIVE WARNING http://commons.wikimedia.org/wiki/Image:DIN_48442_Warnung_vor_Aetzenden_Stoffen_D-W004.svg
10. BE SAFE http://freeclipartnow.com/signs-symbols/warnings/safety-hands.jpg.html
11. ACETIC ACID http://commons.wikimedia.org/wiki/File:Acetic_acid_structures.png
12. NAOH http://wikimediafoundation.org/wiki/File:NaOH.gif