CCA Titration of Second Vinegar with Sodium Hydroxide Lab Report

Chemistry 111Chapter 4
1a. To analyze the alcohol content of a certain wine a chemist needs 1.00 L of an aqueous 0.200 M
K2Cr2O7 solution. How much solid K2Cr2O7 must be weighed out to make this solution.
b. How much of the potassium dichromate solution you made in part a would you need to use to make
250.0mL of a 0.075M solution. ( Be careful you are not starting from scratch you are using the solution
you made in part a of this problem.)
2. Give the balanced molecular, total ionic, and net ionic equations for the reaction of lead (II) nitrate and
sodium sulfate.
3. You wish to determine the molarity of K+ ions in a 50.0 mL sample of K3PO4. To do this you
completely react the potassium phosphate with calcium nitrate. Upon completion you obtain 0.542 grams
of calcium phosphate. Determine the molarity of K+ ions in the original solution.
2K3PO4(aq) + 3Ca(NO3)2(aq) → 6KNO3(aq) + Ca3(PO4)2(s)
4. In a titration, a sample of H2SO4 solution with a volume of 15.00 mL required 36.42 mL of 0.147 M
NaOH for complete reaction. What is the molarity of the H2SO4 solution?
5. The products of an acid-base reaction are water and LiClO4 salt. Give the original acid and base of the
reaction and write the balanced equation for the reaction.
6.For the following equation give the oxidation numbers, show the oxidation and reduction half reactions,
identify the oxidizing agent and the reducing agent.
Cu + NO3- → Cu2+ + NO
7. For the following equation give the oxidation number, show the oxidation and reduction half reactions,
identify the oxidizing and reducing agent.
HNO3 + H3AsO3 → NO + H3AsO4 + H2O
8. Determine the reaction type for each.
a. 2Li(s) + Br2(g) → 2LiBr(s)
b. HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq)
c. CuSO4(aq) + Mg(s) → Cu(s) + MgSO4(aq)
d. Fe(NO3)3(aq) + 3NaOH(aq) → 3NaNO3(aq) + Fe(OH)3(s)
e. NH3(g) + HI(g) → NH4+(aq) + I-(aq)
9. On the basis of the solubility rules suggest a method by which you might separate
NH4+ from Ca2+
10. What is the molarity of Na+ ions in a solution of 25.0 mL of 1.25 M NaCl and 145 mL of 0.550 M
Na2SO4 and 30.0 mL of 0.225 M Na3PO4? Assume the volumes are additive.
11. Barium hydroxide, often used to titrate weak organic acids, is obtained as the octahydrate, Ba(OH)2 .
8H2O. What mass of Ba(OH)2 . 8H2O would be required to make 500.0 mL of a solution that is 0.1500 M
in OH -.
12. A sample of 0.6760 g of an unknown compound containing barium ions (Ba2+) is dissolved in water
and treated with an excess of Na2SO4. If the mass of the BaSO4 precipitate formed is 0.4105 grams, what
is the percent by mass of Ba in the original unknown compound?
1. In an autoclave, steam at 100 oC is generated at 1.00 atm. After the autoclave is closed the steam is
heated at constant volume until the pressure gauge indicates 1.13 atm. What is the new temperature in
the autoclave?
2. A small air bubble rises from the bottom of a lake, where the temperature and pressure are 8 oC and
6.4 atm, to the water’s surface, where the temperature is 25 oC and 1.0 atm. Calculate the final volume
(in mL) of the bubble if its initial volume was 2.1 mL.
3. Sodium azide (NaN3) is used in some air bags in automobiles. The impact of the collision triggers the
decomposition of sodium azide as follows:
2NaN3(s) → 2Na(s) + 3N2(g)
The nitrogen gas produced quickly inflates the bag between the driver and the windshield. Calculate the
volume of nitrogen gas generated at 21 oC and 823 mm Hg upon the decomposition of 60.0 g of sodium
azide.
4. What is the density of carbon tetrachloride gas (CCl4) at 714 torr and 125 oC?
5. A gas in under 1.0 atm of pressure in a flexible container with a volume of 0.50L at a temperature of
393 K. When the gas is heated to 500 K and the volume expanded to 3.0 L, what will the new pressure
be?
6. If you have 5.0 g of CO2 gas in a 10.0 liter vessel at 350 K, what is the pressure?
7. Argon is an inert gas used in light bulbs to retard the vaporization of the filament. A certain light bulb
contains argon at 1.20 atm, and 18 0C is heated to 85 0C at constant volume. Calculate its final
pressure in atm.
8. If you were to prepare oxygen and collect it over water and 10 oC and a total pressure of 748 torr, what
would be its partial pressure?
9. Suppose you have a one-liter container of oxygen gas at two atmospheres pressure and a two-liter
container of nitrogen gas at one atmosphere of pressure. If you transfer the oxygen to the container
holding the nitrogen. What pressure would the oxygen exert? What would be the total pressure exerted by
the mixture?
10. Chemical analysis of a gaseous compound showed that it contained 33.0 percent silicon and 67.0
percent fluorine by mass. At 35 degrees Celsius, 0.210 L of the compound exerted a pressure of 1.70 atm.
If the mass of 0.210 L of the compound was 2.38 g, calculate the molecular formula of the compound.
11. If 24.15 mL of 0.1160M HCl is mixed with 18.60 mL of 0.1312 M NaOH, the two react to form two
new products.
a) Write the Molecular, Total Ionic and Net Ionic Equations for the reaction and identify what type
of reaction this is.
b) Which reactant is the limiting reactant?
c) How many grams of each product are formed?
d) How many millimoles of the reactant that is in excess are left over?
e) Assuming that the volumes of the solutions are strictly additive when they are mixed, what is the
molarity of the unreacted solute in the final solution?
f) Is the solution after the reaction is complete acidic or basic?
12. Battery acid has a density of 1.285 g/cm3 and contains 38.0% sulfuric acid by mass. How many grams
of pure H2SO4 are contained in 1.00 L of battery acid?
13. An ancient gold coin is 2.2 cm in diameter and 3.0 mm thick. If the density of gold is 19.3 g/cm3,
what is the mass of the coin in grams? Assume the price of gold is $1600 per troy ounce. How much is the
coin worth?
14. 106Pd2+ has ____________protons ____________neutrons _____________ electrons
15. Consider the following gaseous sample in a cylinder fitted with a movable piston. Initially there
are n moles of the gas at temperature T, pressure P, and volume V.
Choose the cylinder that correctly represents the gas after each of the following changes.
(1) The pressure on the piston is tripled at constant n and T.
(2) The temperature is doubled at constant n and P.
(3) n moles of another gas are added at constant T and P.
(4) T is halved and pressure on the piston is reduced to a quarter of its original value.
16. A certain hydrate has the formula MgSO4 . xH2O. A quantity of 54.2 g of the compound is heated
in an oven to drive off the water. If the steam generated exerts a pressure of 24.8 atm in a 2.00
Liter container at 120 oC, calculate x.
Determination of Acetic Acid Concentration in Vinegar using Titration: Data
Sheets, Post Lab Questions and notes from Martha
➢ Make sure to read the lab handout and all Safety Instructions thoroughly before doing
the lab. Wear your safety googles, chemical apron and gloves at all times while
conducting this lab.
➢ You are working with toxic chemicals for this lab. You should not eat, drink, chew gum,
or do this lab around children. Make sure to do this lab away from an area where you
have food, and thoroughly clean the area once you are finished.
➢ Wear your safety goggles and your gloves when performing the lab.
➢ You will notice that when you open the lab handout that there are parts of it that are
highlighted in a light orange color these are the parts that you can ignore. We have not
covered pKa in this class, that is a topic for CHE112, so we will not be doing Activity 3 or
reading any of the background on pKa.
➢ See your Chapter 4 notes for more explanation of titration. It is under the acid-base
reactions section of your notes.
➢ This lab really will take you about 1.5 -2 hours to do it carefully and correctly.
➢ You MUST use the chart I have provided NOT the chart that came with the lab handout.
You do not need to take pictures you will just be turning in the data tables and post lab
questions attached to this handout.
➢ Be careful, drops may hang off the end of the syringe between adding drops to the
sample you are titrating, and you don’t want to spray them around your work area.
➢ Practice going slow with the syringe with water before you start the titration, so that
when you are actually doing the titration you are good at it. As little as 1 drop will cause
the color change, so your results will be inaccurate if you can’t add one drops at a time.
➢ If you did a titration in high school or CHE101 using phenolphthalein you may be used to
the color change from clear to very light pink. This is possible using a burette in the lab,
but it is not really possible using the syringe so don’t be surprised your solution goes
from clear and colorless to a very bright pink with just one drop.
➢ HAVE FUN!!!!!
Data Table 1: Titration of Vinegar with Sodium Hydroxide
Vinegar Sample 1
Mass of Vinegar (g)
Volume of Vinegar (mL)
Density = 1.005 g/mL
Initial NaOH volume in
syringe (mL)
Final NaOH volume in
syringe (mL)
Volume of NaOH delivered
(mL)
Volume of NaOH delivered
(L)
Molarity of NaOH
Moles of NaOH delivered
Reaction of NaOH with
Acetic Acid
Moles of Acetic Acid in
vinegar sample
Molar mass of Acetic Acid
Mass of Acetic Acid in
vinegar sample
Calculated Molarity of Acetic
Acid in vinegar sample
Average Molarity
Calculated Percent Mass of
Acetic in vinegar sample
Average % mass
Vinegar Sample 2
Vinegar Sample 3
Data Table 1: Titration of Second Vinegar with Sodium Hydroxide
Identity of your Vinegar Sample _____________________________
Vinegar Sample 1
Mass of Vinegar (g)
Volume of Vinegar (mL)
Density = 1.005 g/mL
Initial NaOH volume in
syringe (mL)
Final NaOH volume in
syringe (mL)
Volume of NaOH delivered
(mL)
Volume of NaOH delivered
(L)
Molarity of NaOH
Moles of NaOH delivered
Reaction of NaOH with
Acetic Acid
Moles of Acetic Acid in
vinegar sample
Molar mass of Acetic Acid
Mass of Acetic Acid in
vinegar sample
Calculated Molarity of Acetic
Acid in vinegar sample
Average Molarity
Calculated Percent Mass of
Acetic in vinegar sample
Average % mass
Vinegar Sample 2
Vinegar Sample 3
POST-LABORATORY QUESTIONS
1.
Suppose you mistakenly wrote out the molarity of NaOH as 1.1 M instead of 1.0 M.
a. Write out the formula for Molarity and solve for moles.
b. Using the equation you wrote out in part c above, determine how the change in
molarity for the NaOH will change the calculation for number of moles used for the
titration.
a. The moles of NaOH used in the titration will be incorrectly high.
b. The moles of NaOH used in the titration will be incorrectly low.
c. The moles of NaOH used in the titration will remain the same
c. Write out the stoichiometric equation for going from moles of NaOH used to grams
of acetic acid.
d.
Using the information from part e above, determine how the percent acetic acid
determined be affected by the incorrect molarity of NaOH used.
a. high
b. Low
c. Unaffected
d. Either high or low
2.
Suppose that my mistake you titrated the acetic acid to a very dark end point.
a.
What does the dark endpoint indicate about the volume of NaOH solution used?
a. Too much NaOH solution is used in the titration
b. Not enough NaOH solution is used in the titration
c. The volume of NaOH solution used in the titration is not affected
d. The amount of NaOH solution used in the titration could be either too high or too
low
b. Write out the formula for Molarity and solve it for moles.
c. Based on the relationship between moles and molarity shown in part b above, what
would any error determined in part a cause in the determination of the moles of
NaOH used in the titration?
a. The moles of NaOH used would be too high
b. The moles of NaOH used would be too low
c. The moles of NaOH used would not be changed
d. The moles of NaOH used could be found as too high or too low
d. Write out the stoichiometric equation for going from moles of NaOH used to grams
of acetic acid.
e. How would the calculated percent acetic acid be changed by any error found in
questions a or c?
a.
b.
c.
d.
3.
The calculated percent acetic acid would be too high
The calculated percent acetic acid would be too low
There would be no change in the calculated percent acetic acid
The calculated percent acetic acid could be found to be either too high or too
low
Suppose you forgot to remove the air bubbles from the tip of your syringe as instructed
by the experimental procedure. Use the type of step-by-step analysis you used in 1 and 2
above to explain what this will do to your calculation of % acetic acid.
CHEMISTRY
Determination of Acetic Acid
Concentration in Vinegar Using Titration
Investigation
Manual
DETERMINATION OF ACETIC ACID IN VINEGAR
Table of Contents
2
Overview
2
Outcomes
2
Time Requirements
3
Background
5
Materials
6
Safety
6
Preparation
7
Activity 1
9
Activity 2
10 Disposal and Cleanup
10 Activity 3
11 Resources
Overview
The goal of this experiment is to accurately determine the
concentration of acetic acid in commercial vinegar. In Activity
1, the percent of acetic acid in the included vinegar sample is
determined. In Activity 2, a different sample of vinegar will be used
and titrated. Activity 3 is a paper activity to calculate the pKa of
the acetic acid based on sample pH data that is provided.
Outcomes
• Calculate the molarity and percent by mass of a solute in
solution.
• Determine the concentration of an acid using titration.
• Understand the role of pH indicators in titrations.
• Calculate the pKa of a weak acid based on experimental data.
• Calculate the percent by mass of a component in a solution.
Time Requirements
Preparation ……………………………………………………………..5 minutes
Activity 1: Titration of Vinegar with Sodium
Hydroxide ………………………………………………………….45 minutes
Activity 2: Titration of Unknown Vinegar Sample with
Sodium Hydroxide ………………………………………………30 minutes
Activity 3: Calculations of pKa from Sample Lab
Data …………………………………………………………………..15 minutes
Key
Personal protective
equipment
(PPE)
goggles gloves apron
follow
link to
video
photograph stopwatch
results and
required
submit
warning corrosion flammable toxic environment health hazard
Made ADA compliant by
NetCentric Technologies using
the CommonLook® software
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Background
Aqueous solutions fall into one of three
categories—acidic, basic, or neutral—depending
on the number of hydrogen ions (H+) and
hydroxide ions (OH–) present. Water molecules
constantly dissociate into H+ and OH–, which then
come back together to re-form water molecules. It
should be noted that the H+ ion does not actually
exist as such in an aqueous solution. Rather, H+
ions will associate with adjacent oxygen atoms,
forming hydronium ions (H3O+).
However, for the sake of convenience in our
discussion of pH, we will refer to H+ rather than
H3O+.
The pH scale ranges from 0 to 14. The neutral
center of the scale, 7, represents the amount of
H+ per liter of water at 25 °C, which is equal to
1 × 10–7 moles. Solutions with a pH of less
than 7 possess more H+ and fewer OH– ions,
and are considered acidic. Solutions with a pH
greater than 7 possess less than 1 × 10–7 H+ (and
therefore more OH–) and are considered basic,
or alkaline. A solution with an equal number of
H+ and OH– is considered neutral. Note that,
because pH values are based upon logarithms
of the base 10, each pH value varies from the
next by a factor of 10 in terms of strength. For
example, a solution with a pH of 5 is 10 times
more acidic than one with a pH of 6.
Logarithms and pH
It is useful to be able to determine the pH of an
aqueous solution if the amount of H+ is known;
likewise, sometimes one knows the pH of the
solution but needs to deduce the amount of H+.
Brackets in an equation, such as [H+] below,
refer to the concentration.
To determine pH when [H+] is known, use the
following formula:
pH = –log[H+]
For example: Determine the pH of an aqueous
solution in which [H+] = 1 × 10–3 M.
pH = –log[H+] = –log(1 × 10–3) = 3
To determine [H+] when the pH of a solution is
known, use the same formula. The notation “inv
log” refers to the inverse log.
For example: An aqueous solution has a pH of
5.5. Determine [H+] in M (moles/liter).
pH = –log[H+] = 5.5
log[H+] = –5.5
[H+] = inv log (–5.5) = 3.2 × 10–6 M
Vinegar, a widely used preservative, cleaning
product, and cooking ingredient, is a solution
of acetic acid (CH3CO2H). Different types of
vinegar are produced through the fermentation
of a wide variety of fruits and grains. Distilled
white vinegar is produced by the fermentation of
alcohol derived mainly from corn.
A titration is the precise addition of a solution
of known concentration and composition,
called the titrant, to a solution of unknown
concentration or composition, called the
analyte. In this acid-base titration, the titrant,
sodium hydroxide, is delivered through a
syringe in order to measure precisely (±0.1 mL)
the volume of base added. In many traditional
acid-base titrations, the titrant is added using
a burette, a piece of glassware designed
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3
DETERMINATION OF ACETIC ACID IN VINEGAR
Background continued
for adding known volumes of a solution to
another container. Acetic acid, a weak acid,
can be neutralized with a strong base, such
as sodium hydroxide, to form a salt and water.
The concentration of acetic acid, the analyte, in
vinegar can be determined through an acid-base
titration.
CH3CO2H + NaOH → NaCH3CO2 + H2O
At the equivalence point of a titration, the
moles of acid added is exactly equal to the
moles of base in the solution before the titration
started. The equivalence point is achieved
when sufficient titrant has been added to react
with all of the analyte. The end point is the
experimental estimate of the equivalence point,
and is typically identified by a color change in
an indicator solution. In a titration, there is a
noticeable change in pH near the end point.
A change in color of an indicator added to the
analyte at the start of the titration is observed
when the end point has been reached. The
molarity and volume of the titrant are known,
as is the volume of the analyte. To determine
the concentration of the analyte, first determine
the number of moles of titrant that were needed
to reach the end point. Next, use the balanced
chemical equation to calculate the moles of
analyte present. Finally, use the volume of the
analyte to find the concentration of the analyte.
The pH range of the indicator used for a given
titration must include the pH change of the end
point. Acid-base indicators are weak organic
acids that change color depending on the pH
of the solution. The pH range of an indicator
is the range of pH values over which the color
change occurs when the indicator converts
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between its acidic and basic forms. This range
depends on the strength of the indicator’s acid
form and, therefore, varies among indicators.
Phenolphthalein is the indicator used in this
experiment. Phenolphthalein is colorless in its
acidic form and pink in its basic form. The pKa
of this indicator is 9, and it has a pH range of
8–10, which is appropriate for the titration to be
performed.
It is important to remember that acids and
bases will dissociate in aqueous solutions.
The acid dissociation constant (Ka ) is the
equilibrium constant of the dissociation reaction
of an acid in aqueous solution, representing a
dynamic balance between the acid in its intact
and dissociated states. The pKa is a simplified
representation of Ka.
The pKa of the acetic acid can easily be
calculated using the data obtained in this lab
and the Henderson-Hasselbalch equation:
pH = pKa + log[A–]/[HA]
pKa = –log Ka
The Ka, the acid dissociation constant, is the
equilibrium constant for the dissociation
reaction:
HA ↔︎ H+ + A–
where an acid (HA) dissociates to form its
conjugate base (A–) and a hydrogen ion (H+).
Because the value of Ka can vary over several
orders of magnitude, it is convenient to use the
–log of this number, the pKa, for reference. In the
pKa equation, [A–] is the molar concentration of
the anion and [HA] is the molar concentration of
continued on next page
the acid. For practical purposes, the pKa should
be equal to the pH at the midpoint of a titration.
The midpoint is the volume that is halfway to the
end point of a titration. At the midpoint, [HA] =
[A-] and the pH measured at the midpoint can
be used to experimentally determine the pKa.
Materials
Included in the equipment kit:
Graduated
cylinder,
10 mL
Erlenmeyer
flask, 25 mL
Plastic cup,
1.25 oz
Electronic
balance
Needed from
the materials
kit:
Needed from
the chemical
kit #1:
Syringe,
10 mL
Vinegar, acetic
acid solution
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5
DETERMINATION OF ACETIC ACID IN VINEGAR
Materials continued
Needed from the chemical kit #2:
Phenolphthalein
indicator
solution, 1%
Sodium
hydroxide
solution, 1 M
Needed, but not supplied:
• Plain sheet of white paper
• Vinegar sample
Activity 1 will be performed using the vinegar
that comes with the kit. Activity 2 will be
performed using a different vinegar sample
to compare concentrations. Find some malt,
rice, or other type of vinegar for the second
titration. Some restaurants have small
packets of malt vinegar as a condiment.
Reorder Information: A replacement kit for
Determination of Acetic Acid Concentration in Vinegar Using Titration, item number
580314, can be ordered from Carolina
Biological Supply Company.
Call 800-334-5551 to order.
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Safety
Wear your safety
goggles, chemical
apron, and gloves at all times while conducting
this investigation.
Read all the instructions for this laboratory
activity before beginning. Follow the instructions closely and observe established laboratory
safety practices, including the use of appropriate personal protective equipment (PPE) as
described in the Safety and Activity sections.
Phenolphthalein is an alcohol based
solution. Keep chemical away from
any heat or flame sources.
Acetic acid and sodium hydroxide
are corrosive. In the event of contact
with skin or eyes, the affected area
should be immediately rinsed with
water for 15 minutes.
Do not eat, drink, or chew gum while performing
this activity. Wash your hands with soap and
water before and after performing the activity.
Clean up the work area with soap and water
after completing the investigation. Keep pets
and children away from lab materials and
equipment.
Preparation
1. Read through the Procedure.
2. Obtain all materials.
3. Clean and sanitize work area.
ACTIVITY
ACTIVITY 1
A Titration of Vinegar with
Sodium Hydroxide
1. Place the 10-mL graduated cylinder on the
electronic balance.
12. Add NaOH dropwise from the syringe, with
constant swirling, until a single drop of
NaOH causes a color change that persists
for a few seconds after the addition. This
indicates that the end point has been
reached.
2. Tare the balance.
To gain more control of single drops from
the syringe, move the plunger by holding
it where it enters the syringe instead of
pressing the end of the plunger.
3. Dispense ~ 5 mL of vinegar into the
graduated cylinder with a plastic pipet.
4. Record the exact mass of vinegar in Data
Table 1.
5. Transfer the vinegar into the clean 25-mL
Erlenmeyer flask.
6.
Add 2 drops of phenolphthalein to
the vinegar. Take photograph of flask
as the start point of the titration.
7. Transfer approximately 10 mL of 1 M
sodium hydroxide (NaOH) to the small cup.
This solution will be used to fill the syringe.
8. Fill the syringe with 1 M NaOH solution.Try
to minimize the amount of air in the syringe.
9. Record the initial volume of NaOH solution
in the syringe to the nearest 0.1 mL in Data
Table 1 for Vinegar Sample 1. Read the
volume of the syringe at the edge of the
plunger.
10. Place the flask containing the 5.0 mL of
vinegar on the white sheet of paper. The
white background will make the color
change more noticeable.
11. Add NaOH from the syringe in 0.5-mL
increments, swirling the flask between
each addition until a color change persists
for a few seconds after the addition of the
NaOH.
13.
Once the end point has been
reached, record the final volume
of NaOH in the syringe in Data Table 1 for
Vinegar Sample 1. Take photograph of flask
as the end point of the titration.
14. Calculate the total volume of NaOH that was
required to reach the end point and record
the data in Data Table 1.
15. Dispose of the titrated vinegar sample in the
sink.
16. Rinse the 25-mL flask three times with water.
17. Repeat steps 1–16 for Vinegar columns 2
and 3 on the Data Table 1.
18. Calculate the concentration of acetic acid
in your vinegar sample based on your
experimental data The molar mass of acetic
acid is 60.05 g/mol. See the following
example:
Example:
A sample of 10.0 grams of HCI solution of
unknown concentration is titrated to the end
point with 6.2 mL of a 1.0 M NaOH sample.
Calculate the concentration of hydrochloric
acid.
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7
ACTIVITY
ACTIVITY 1 continued
1. Calculate the volume of HCl solution.
Volume = Mass / Density
Volume = 10.00 g / 1.00 g/mL = 10.00 mL
2. Determine the moles of sodium hydroxide
used to reach the end point.
Moles of NaOH = 1.0 M × 6.2 mL × 1 L /
1,000 mL = 0.0062 moles NaOH
3. Determine the moles of hydrochloric acid in
the sample.
Moles of NaOH = Moles of HCl at the
equivalence point
Moles of NaOH = 0.0062 moles = Moles of HCl
4. Calculate the molarity of hydrochloric acid.
0.0062 moles / 0.010 L = 0.62 M HCl
5. Calculate the mass of hydrochloric acid in the
initial sample.
Mass of HCl = Moles of HCl / Molar Mass of HCl
Mass of HCl = 0.0062 mol × 36.46 g/mol = 0.23 g
6. Calculate the percent mass of hydrochloric acid
in the initial sample.
Percent Mass = (Mass of Solute / Total mass) ×
100
Percent Mass = (Mass of HCl / Mass of solution)
× 100
Percent Mass = (0.23 g / 10.00 g) x 100 = 2.3 %
Data Table 1: Titration of Vinegar with Sodium Hydroxide
Name of Vinegar Sample
Mass of Vinegar
Volume of Vinegar Density
= 1.005 g/mL
Initial NaOH Volume in Syringe
Final NaOH Volume in Syringe
Volume of NaOH Delivered
Moles of NaOH Delivered
Moles of Acetic Acid in Sample
Mass of Acetic Acid in Sample
Calculated Molarity of Acetic Acid in
the Sampled Vinegar
Calculated Percent Mass of Acetic
Acid in Sampled Vinegar
Average Calculated Percent Mass
of Acetic Acid in Sampled Vinegar
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Vinegar Sample 1 Vinegar Sample 2 Vinegar Sample 3
ACTIVITY 2
A Titration of an Unknown Vinegar
Sample with Sodium Hydroxide
Activity 2 is an inquiry-based activity to demonstrate the learned technique of determining
the acetic acid concentration in vinegar to a
vinegar sample from your home. Each type of
vinegar has a slightly different concentration
of acetic acid. This activity requires the selec-
tion of a vinegar product from your home, a
friend’s home, or a local restaurant. Only about
a teaspoon of vinegar is needed. Attempt to find
a different type of vinegar such as cider, malt, or
balsamic vinegar. The vinegar included in this kit
is white vinegar. Different brands of vinegar may
also contain different amounts of acetic acid.
Use the same procedure and Data Table 2
to determine the acetic acid content in your
vinegar sample.
Data Table 2: Titration of Second Vinegar Sample with Sodium Hydroxide
Name of Vinegar Sample
Vinegar Sample 1 Vinegar Sample 2 Vinegar Sample 3
Mass of Vinegar
Volume of Vinegar Density
= 1.005 g/mL
Initial NaOH Volume in Syringe
Final NaOH Volume in Syringe
Volume of NaOH Delivered
Moles of NaOH Delivered
Moles of Acetic Acid in Sample
Mass of Acetic Acid in Sample
Calculated Molarity of Acetic Acid in
the Sampled Vinegar
Calculated Percent Mass of Acetic
Acid in Sampled Vinegar
Average Calculated
Percent Mass of Acetic Acid in
Sampled Vinegar
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9
ACTIVITY
Disposal and Cleanup
solve a mathematical problem. The pKa of acetic
acid is 4.75, and the volume of vinegar is 21.05
mL.
1. Dispose of titrated samples in the sink.
2. Clean and dry the flask and return it to the
equipment kit.
3. Return unused chemicals to the chemical kit.
4. Sanitize work space.
1. Review the lab data found in Data Table 3.
This is from a titration of a vinegar sample
using a pH meter.
2. Determine the volume of 0.1 M NaOH
dispensed during the titration. Record the
answer.
ACTIVITY 3
3. Calculate the molarity of the acetic acid in the
vinegar samples. Record the answers.
A Calculations of pKa from
Sample Lab Data
The following activity is intended as an extension
activity and requires the application of concepts
from the Background and Activities 1 and 2 to
4. Calculate the pKa of acetic acid from
the midpoint data using the HendersonHasselbach equations in the Background
section.
continued on next page
Data Table 3: Titration of Vinegar with Sodium Hydroxide
Vinegar Sample 1 Vinegar Sample 2 Vinegar Sample 3
Initial pH Reading
pH = 3.211
pH = 3.102
pH = 3.105
Initial Buret Reading
2.89 mL
3.00 mL
1.61 mL
Midpoint pH Reading
pH = 4.895
pH = 4.687
Midpoint Buret Reading
12.92 mL
9.50 mL
Final pH Reading
pH = 8.238
pH = 8.531
pH = 8.934
Final Buret Reading
20.12 mL
20.31 mL
19.00 mL
Volume of NaOH dispensed
Calculated Molarity of Acetic Acid in
the Vinegar Sample
Volume NaOH dispensed at
Midpoint Reading
Moles of NaOH Consumed at
Midpoint Reading [A–]
Moles of Acetic Acid Remaining at
Midpoint [HA]
Calculated pKa
10
Carolina Distance Learning
ACTIVITY 3 continued
5. Find the average calculated molarity, percent
by mass concentration, and pKa for acetic
acid based on the provided data.
Average calculated molarity of acetic acid:
_________________________________________
Resources
Setting up and Performing a Titration
http://www.carolina.com/teacherresources/Video/setting-up-andperforming-a-titration-video/tr11191.tr
Titration Calculations
http://www.carolina.com/teacherresources/Video/titration-calculationsvideo/tr11190.tr
Average acetic acid concentration
expressed in percent by mass:
_________________________________________
Average value of pKa of acetic acid based on
provided experimental data:
_________________________________________
Percent error for pKa of acetic acid:
_________________________________________
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11
CHEMISTRY
Determination of Acetic Acid Concentration in Vinegar Using Titration
Investigation Manual
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