Lab 4 Final
Lab 4 Final
Lab 4 Final
Group No
Group Rashed Alhammadi H00513007
Members
Saoud Alkazeeri H00392071
Note: Students are expected to refrain from all forms of academic dishonesty as defined in the
college policies and as explained and defined by college policies, procedures, and directions from
teachers or other college personnel. By signing this cover page, you are stating that the work
presented is yours and yours alone. The work includes all figures, tables, calculations, data and text.
Please note only reports that include a signed cover sheet will be graded.
I hereby state that all work submitted in this report is mine and solely mine.
2. Theory:
Titration is a chemical technique, which has been used to determine the unknown concentration
of a known solution. In acid-base titration, an unknown concentration of a base can be
determined by titrating it against a volume of a known concentration of an acid which is known
as standard solution. Such type of reaction is a known as neutralization reaction, where salt and
water are produced.
The indicator is a chemical substance that has different colors in both acidic and alkaline media.
The colour change depending on the pH of the solution. The pH indicator colour change will be
shown when the reaction has completely neutralized (neutralization point or equivalence point).
This point, will be reached when all acid was consumed and there is no excess of base. When
the equivalence point is reached, we will be able to determine the concentration of the unknown
acid using a series of calculations normally three titrations and average the trials.
1. Molarity (M) or molar concentration is the unit for measuring the concentration of solutions. It
is defined as the number of moles of solute in a liter of solution.
2. Titrant: The solution of known concentration and is also called the standardized solution. In
This lab, the titrant is HCl solution.
Burette pipette/pipette bulb Erlenmeyer
(conical) flask titration setup
3. Burette a long, cylindrical glass that can be used to determine accurate quantities of a solution
and it is controlled by a Teflon or a glass stopcock.
4. Volumetric pipette/pipette bulb: is a thin glass tube used to accurately measure a specific
volume of liquid.
5. Indicator: is the chemical substance that has different colors in both acidic and basic solutions.
Safety Notes:
a. Safety goggles must be worn at all times in the lab.
c. All chemicals are hazards (They can burn your skin, eyes, clothes), and treat all chemicals
as toxic.
1. In this experiment, you are required to determine the molarity of the unknown concentration
of NaOH solution. Use NaOH solution as a analyte and standard acid HCl solution as titrant
until you reach the endpoint. A standard acid solution HCl of 0.105 M will be provided.
2. The experiment is already sited in bench.
3. Before you start, rinse the 50 mL burette with deionized water, and then twice with about 5
mL of the hydrochloric acid solution.
4. Fill the burette with HCl solution to just above the zero mark without having any bubbles out
of the tip of the burette.
5. Adjust the HCl solution mark at zero mark, read, and record the burette reading to the
nearest
0.02 mL.
6. Add 20.0 mL of the NaOH solution using the graduated cylinder in three clean Erlenmeyer
flasks separately.
7. Add 2 or 3 drops of phenolphthalein to each of Erlenmeyer flasks. A pink color appears.
8. Place one flask on the stand underneath the burette, and start adding HCl drop by drop from
the burette spinning (shake) the flask constantly and recognize any color change.
9. By approaching the endpoint, the pink color starts to disappear, this indicating a local excess
of the HCl, which will increase in size.
10. Once you see the pink spot, slow down the rate of adding HCl.
11. Once no colored solution becomes stable, Stop adding HCl solution, this is the endpoint.
12. Read the burette to the nearest 0.02 mL and record the reading in the provided table.
13. Repeat the same process with the other two flasks and record the reading in each experiment.
14. Calculate the molarity of the NaOH solution separately for each titration.
𝟎.𝟏+𝟎.𝟏+𝟎.𝟏
AVERAGE MOLARITY OF NaOH = 𝟎. 𝟏 𝑴 [5 marks]
𝟑
1. How do you tell if you have exceeded the equivalence point in your titration? [5 marks]
In our titration, we find the concentration of an unknown base (NaOH) by reacting it with a known
acid (Hcl) solution. This produces salt and water. To mark the endpoint, we use a pH indicator like
phenolphthalein, which turns pink in a basic solution. The color should be very faint to achieve
accuracy. The unknown acid's concentration is calculated based on the volume of acid used at the
endpoint, typically after multiple experiments. Other methods also :
▪ Color Change: Many titrations involve the use of an indicator, like phenolphthalein,
which changes color at or near the equivalence point.
▪ Change in Volume: By closely monitoring the volume of titrant you've added, you can
determine if you've gone beyond the equivalence point. If you continue to add titrant
even after the desired endpoint is reached, you'll see an excess volume in your burette
reading.
▪ Change in Signal: In some advanced titrations, automated systems may use sensors to
detect changes in properties like electrical conductivity or potential. These sensors will
indicate changes once you've passed the equivalence point.
2. If 25.00 mL of hydrochloric acid with 0.05 M is titrated against 0.15 sodium hydroxide solution.
what is the volume of the sodium hydroxide needed for neutralization? [10 marks]
So, we would need 8.33 mL of 0.15 M of NaOH solution to neutralize 25 mL of 0.05 M of Hcl
solution.
In another way M1V1=M2V2
3. What is the concentration of 10.00 mL of H2SO4 if it takes 66.37 mL of a 0.205 M KOH solution
to neutralize it? [10 marks]
H2SO4 + 2KOH → K2SO4 + 2H2O
▪ Methyl Orange: Methyl orange changes from red to yellow as the pH shifts from acidic
to slightly basic. It is often used in strong acid-strong base titrations.
▪ Alizarin Yellow: Alizarin yellow changes from yellow to red as the pH increases,
making it suitable for titrations in the pH range of about 10 to 12.
▪ Thymol Blue: Thymol blue goes from red to yellow and then to blue as the pH
increases, allowing it to be used over a range of pH values.