SCH 4C
Summative - QUANTITATIVE TITRATION - Part 1
PURPOSE: Design a procedure to make a 0.300mol/L solution of NaOH from solid NaOH
pellets.
MATERIALS:
Solid NaOH
Electronic Balance
Distilled water
Safety goggles
250ml or 500ml volumetric flask with stopper
Scrap Paper
SAFETY PRECAUTIONS:
The NaOH solution is corrosive to skin, eyes and clothing. Do NOT handle the pellets with your
skin. Wash any spills or splashes immediately with plenty of water. Wash your hands thoroughly
after handling the chemicals.
PRE-LAB CALCULATIONS and PROCEDURE:
Pure NaOH (s) is often used to create a solution of a known concentration. In order to create the
solution from a solid, you must first calculate the amount of pure NaOH to be used.
Before you start, you must first outline a step by step method to obtain the proper amount of solid
to make a solution of a known concentration knowing your knowledge of quantitative relationships
of mass, moles and molar mass. When a solid base (NaOH) is added to distilled water, a solution
of a base is created. Concentration is equal to the moles of a substance divided by the liters of the
substance as a liquid. C = n / V
Today you will have time to write the procedure in rough, and do the procedure to make the
solution. You will need to write the procedure again as part of your formal lab write-up.
1. Write the procedure on a separate sheet of paper showing all steps and calculations to be done in
order to obtain the proper amount of solid.
2. Write a step by step procedure for mixing the solid with the liquid. Be sure to include a step to
label the solution with the experimenters names for use in Part 2.
SCH 4C
Summative - QUANTITATIVE TITRATION - Part 2
Names:
Relative amounts of reactants and products of a reaction are commonly investigated in two
ways in the laboratory: gravimetrically (by mass) and volumetrically (by volume and
concentration) as in this experiment. Titration is the name given to the process of determining the
volume of a solution needed to react with a given mass, or volume, of a sample. We shall use this
process to study quantitatively the reaction between an acid and a base.
Acid-base titrations involve the neutralization reaction between aqueous hydrogen and
hydroxide ions. These ions combine to form the neutral water molecule:
H + (aq) + OH – (aq) → H2O (l)
Recall that indicators may be used to determine of the hydrogen ion concentration. The point at
which an indicator changes colour is called the endpoint, indicators change colour at a specific
pH. Phenolphthalein will be used as the indicator in this experiment since its colour change occurs
when an equal number of moles of acid and base have been added. This point in the reaction is
called the equivalence point.
At neutralization the concentration of H + and OH – are the same and the equivalence point has
been reached. The total number of moles of acid or base reacting can be calculated by
manipulating the following equations:
C = n/V
or
VaCa = VbCb.
Vinegar is a dilute solution of acetic acid, CH3C–OH. Only the hydrogen atom that is
attached to an oxygen atom is acidic. Thus, acetic acid contains only one acidic hydrogen. As a
consumer, you can buy vinegar with different concentrations. For example, the concentration of
table vinegar is different from the concentration of the vinegar that is used for pickling foods. To
maintain consistency and quality, manufacturers of vinegar need to determine the percent
concentration of acetic acid in the vinegar. In this investigation, you will determine the molarity of
acetic acid in a sample of vinegar. In addition, you will calculate the percentage, by mass, of the
vinegar. The mass of the acetic acid (CH3COOH) in the vinegar is obtained from a mole-mass
calculation. The mass of the solution is obtained from the measured volume of the solution times
its density (D = m/V). For this experiment, you may assume that the density of the vinegar is 1.01
g
/mL.
Titration is one of the most common operations performed by the chemist. We all depend
upon chemical analysis, and it is with this branch of chemistry that the average citizen is most
likely to come into contact. Decisions involving huge sums of money, or even life and death,
depend upon the accuracy and speed of chemical analysis, whether in hospital lab testing,
environmental pollution monitoring, or crime detection.
QUANTITATIVE TITRATION
PURPOSE: To determine the concentration and percent composition of a sample of vinegar.
HYPOTHESIS: Make a guess as to the molarity of vinegar and its percent composition by mass.
MATERIALS
retort stand
burette clamp
phenolphthalein
burette
250 mL beaker
distilled water
funnel
250 mL Erlenmeyer flask
vinegar
safety goggles
0.300 M NaOH (aq)
SAFETY PRECAUTIONS
The NaOH solution is corrosive to skin, eyes and clothing. Wash any spills or splashes
immediately with plenty of water. Phenolphthalein is poisonous and flammable. Do not get any
in your mouth; keep well away from flame. The vinegar solutions are mildly corrosive. Keep
them off your skin and out of your eyes. Wash any spills and splashes immediately with plenty of
water.
PROCEDURE
1. See the section on the care of burettes at the end of this experiment. Set up a retort stand,
burette clamp, burette, and funnel. Rinse the burette first with distilled water. Then rinse it
with 10 mL sodium hydroxide solution. After rinsing the burette, fill it with the base. Make
sure that there are no air bubbles in the burette. Also make sure that the liquid fills the tube
below the glass tap. Remove the funnel before beginning the titration. Record the volume in
the burette by reading the bottom of the meniscus to the nearest 0.01 mL.
2. Go to the burette set up at the side of the room and add 10.00 mL of vinegar into a 250 mL
Erlenmeyer flask. Record this amount. Add approximately 15.0 mL of water. Also add half
an eyedropper of phenolphthalein indicator.
3. Place a sheet of white paper under the Erlenmeyer flask. Hold the neck of the Erlenmeyer
flask with one hand and manipulate the burette with the other. As you add the sodium
hydroxide, gently swirl the flask so the solutions will become mixed. Continue adding sodium
hydroxide until the first faint pink colour develops. If the colour disappears upon mixing the
solution, add more sodium hydroxide, drop by drop, until a persistent pale pink colour is
obtained. If you are not sure whether you have reached the end-point, take the burette
reading. Add one drop of sodium hydroxide, or part of a drop. Observe the colour of the solution. (Take care not to go beyond the last calibration marks on the burette.) Record the
volume reading at the bottom of the meniscus of the burette. Rinse the Erlenmeyer flask
thoroughly before repeating the titration.
4. Repeat the titration until you obtain volumes of base that are within 0.5 mL of each other.
5. When you have finished, dispose of the chemicals as directed. Rinse the pipette and burette 3
times each with water. Leave the burette tap open.
REAGENT DISPOSAL
Mix any leftover acids and bases together to neutralize, and pour down the sink with plenty of
water. Do not return any solutions to their original containers.
DATA AND OBSERVATIONS
Determination of Concentration and Percent Composition of Vinegar
Trial 1
Concentration of NaOH
Volume of vinegar (mL)
Initial volume of NaOH
(mL)
Final volume of NaOH (mL)
Volume of NaOH used (mL)
Trial 2
Trial 3
Trial 4
CALCULATIONS
1 a) Write the balanced chemical equation for the reaction of acetic acid with sodium hydroxide.
b) According to the equation, how many moles of acetic acid are used per mole of base?
c) Using the relationship in b), calculate the moles of acetic acid used.
2. a) Calculate the molarity of acetic acid in your vinegar sample. Use the average volume and
concentration of sodium hydroxide, and the volume of vinegar.
3. a) Find the molar mass of acetic acid.
b) Calculate the mass of acetic acid in the volume of vinegar you used.
c) The density of vinegar is 1.01 g/mL. Calculate the mass of the vinegar sample.
d) Find the percent, by mass, of acetic acid in the vinegar sample.
Discussion
1. a) Explain the difference between the equivalence point and endpoint of a titration.
b) What was the reason for rinsing out the burette with NaOH solution before starting the
titrations?
c) While doing a titration, it is permissible to use a wash bottle of distilled water to wash down
any material that may have splashed higher up. This would appear to increase the volume of
the acid in the flask. Why will it have no effect on the results?
2. a) By law, vinegar must be not less than 4% by mass acetic acid. Did your sample meet this
specification? Explain.
b) List several possible sources of error in the experiment.
3. Most shampoos are basic. Why do some people rinse their hair with vinegar after washing it?
Conclusions: One sentence please.
CARE OF BURETTES
Cleaning
Place a few milliliters of a detergent solution into a burette, then use a burette brush to clean
the inside surface. Rinse well, first with tap water and then with distilled water. After draining the
burette, note if there are any droplets still adhering to the sides of the tube. If there are, the glass is
not thoroughly cleaned and should be rewashed. When glass is clean, water wets it evenly.
Preparing for Use
After cleaning a burette, add 5—10 mL of the solution that is to be used in that burette. Let
several milliliters of solution flow through the tip. Turn the burette to a horizontal position and
with a rotary motion, slowly pour the rest of the solution out of the top. Make sure that the
solution wets the inside completely. For a more complete rinsing, repeat the above.
Fill the, burette to the top with the solution to be used. Let solution flow from the tip until the
bottom of the meniscus is at zero or below. This should eliminate air bubbles in the tip.
If a drop hangs on the tip before you start a titration, discard it by touching it to a beaker.
However, a drop formed during a titration must be caught by touching it to the side of the
container being used and rinsing it into the container with distilled water.
Reading the Volume
When reading the volume on the burette, be sure to have your eye level with the bottom of the
meniscus and read the volume carefully at the bottom of the curve. In each titration use an
absolute minimum of 10 mL of each solution to attain a precision of 1.0 %.
After Use
Drain and rinse the burette several times with tap water, then, as a final rinse, use distilled
water. Glass reacts with basic solutions so take special care in rinsing a burette that has had such
solutions in it. A rinse with dilute acid after one water rinse will help assure that the base is
removed. Follow this with the water rinses described above. Leave the stopcock open when
storing the burette.
Quantitative Lab Rubric
Student Name: ____________________
Level 4
Overall Expectation
Demonstrate an understanding of
the basic principles of qualitative
analysis and underlying theories
Carry out qualitative analysis,
using flow charts and appropriate
laboratory equipment instruments
Describe the role and importance
in society of some of the
applications of qualitative
analysis.
Demonstrate an understanding of
the mole concept as well as of
quantitative relationships in
chemical reactions
Use techniques of quantitative
analysis in the preparation of
standard solutions, and solve
problems involving the analysis of
quantities in chemical reactions,
using both theoretical and
experimentally measured
quantities
Explain the importance of
quantitative chemical relationships
in industry and in everyday life.
Use the techniques involved in the
quantitative analysis of solutions
effectively and accurately;
?Guiding Question?
Have I clearly demonstrated
my knowledge of qualitative
analysis and related that to
theories that explain what I
observed?
Have I logically and clearly
followed qualitative
observations through to
interpret the observation and
make conclusions?
Have I related what I have
observed and the principles
learned to useful applications
in real life?
Have I clearly shown proper
manipulation of mole and
“hub” calculations to obtain
useful data from my
quantitative observations?
Have I properly prepared a
standard solution using
proper technique?
Level 3
Level 2
Level 1
To a moderate
degree
To a
limited degree
To an
exceptional
degree
4++ 4+ 4 4-
To a
considerable
degree
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
4++ 4+
4
4-
3+
3
3-
2+
2
2
1+
1
1-
Not
Yet
Have I followed all
instructions correctly to use
the apparatus and materials
in the experiment?
Have I related the
calculations and/or
procedure to an industrial or
commercial application?
Have I observed, recorded,
analyzed, and communicated
results of an inquiry with a
high degree of clarity?
Mark: ________________
You are to include the following in your final word processed lab report in 12 point Times New Roman Font
including Title Page:
 Procedure for finding the proper amount of NaOH to mix
 Procedure to mix the solution of NaOH
 Observations of your titration
 Calculations showing all intermediary work
 Answers to discussions in typed format
 A Conclusion
 Bibliography of any research you completed