CHEM 2204 – Chemical Laboratory Techniques
Practical Lab Techniques Datasheets
Technique #1 – Use of a Burette
Technique #2 – Use of a Pipette
Technique #3 – Use of a Volumetric Flask
Technique #4 – Weighing
Technique #5 – Use of a Bottle-Top Dispenser
Technique #6 - Gravity Filtration, Vacuum Filtration
Technique #7 – Preparation of a Standard Solution
Technique #8 – Titration
Instructions to students:
Students should refer to the “Demonstrations of the Eight Practical Lab
Techniques” document when attempting to complete all the tasks outlined for
each technique. By the end of the lab, it is expected that you will be able to carry
out all the tasks using the proper chemical laboratory techniques.
Study the photos and diagrams carefully. Pay close attention to the assembly of
the apparatus and how each piece of glassware is positioned relative to each other.
If you are uncertain about a technique, consult your instructor.
When recording data on the datasheet, record the data directly in pen, and record
the data using the proper number of significant figures.
Jan 04, 2011
Page 1
Technique #1 – Use of a Burette
Task:
1. Prepare and fill the burette with the solution provided.
2. Record the initial burette reading.
3. Place an Erlenmeyer flask under the burette to receive the solution from the
burette.
4. Using the timer provided, open the stopcock for approximately 15 seconds.
5. Record the final burette reading.
6. Determine the volume of the solution delivered into the Erlenmeyer flask.
Datasheet:
1. Final Burette Reading
______________________
2. Initial Burette Reading
______________________
3. Volume of solution delivered
______________________
Jan 04, 2011
Page 2
Technique #2 – Use of a Pipette
Task:
1. Choose a volumetric pipette from the selection of volumetric pipettes available.
2. Determine the volume that the volumetric pipette can hold.
3. Using the pipette chosen, transfer the volume of a solution provided into an
Erlenmeyer flask.
4. Enter the volume of the solution that has been transferred into the beaker in the
datasheet.
Datasheet:
Volume of the solution in the beaker
Trial 1: ______________________
Trial 2: ______________________
Trial 3: ______________________
Jan 04, 2011
Page 3
Technique #3 – Use of a Volumetric Flask
Solutions are often prepared by dilutions of a stock solution. The concentration of the
stock solution, Ci, is given on the reagent bottle. The dilution equation is
CiVi = CfVf
Equation (1)
where
Ci = concentration of the stock solution
Vi = volume of the stock solution
Cf = final concentration of the dilute solution
Vf = final volume of the dilute solution
The dilution factor, D is
D = Ci / C f .
Equation (2)
Example: Prepare a 100.0 mL of a solution by diluting the stock solution provided by a
dilution factor of 30. The concentration of the stock solution is 2.010 M.
To calculate the final concentration of the dilute solution, let Ci=2.010 M and let D= 30.
Substitute Ci and D into equation (2) and solve for Cf, the concentration of the dilute
solution.
30 = 2.010 M / Cf
Cf = 2.010 M / 30 = 0.06700 M
The concentration of the dilute solution is 0.06700 M.
Use Equation (1) to determine the volume of the stock solution, Vi, needed.
(2.010 M) Vi = (0.06700 M) (100.0 mL)
Vi = 3.333 mL
Planned action: To prepare a 0.4020 M solution, withdraw 3.333 mL from the 2.010 M
stock solution and transfer this quantity into a 100 mL volumetric flask. Make up to the
mark with distilled water and mix thoroughly.
Jan 04, 2011
Page 4
Task:
1. You are asked to dilute the stock solution, Solution A, by the dilution factors
given in the table below. Each diluted solution has a final volume of 100.0 mL.
The Stock solution, Solution A, is 2.010 M.
Using Equations (1) and (2), calculate Cf and Vi. Fill out the table below.
Dilution
Factor
Ci
(M)
Cf
(M)
Vi
(mL)
Vf
(mL)
2
2.010
_______
_______
100.0
5
2.010
_______
_______
100.0
10
2.010
_______
_______
100.0
2. Reach your hand into the box and draw a dilution factor.
3. Using the calculated values, prepare 100.0 mL of the dilute stock solution.
Your Planned action:
|
To prepare a _____________ M (Cf) solution, withdraw ___________ mL (Vi)
from the 2.010 M stock solution and transfer this quantity into a 100 mL volumetric
flask. Make up to the mark with distilled water and mix thoroughly.
Jan 04, 2011
Page 5
Technique #4 – Weighing
Task: Weigh a sample of sand
1. Weigh by taring a sample of sand that is approximately 0.5 g. Transfer the sand
sample into a beaker.
2. Enter your mass measurements into the datasheet.
3. When you are finished, return the sand to the bottle provided and wipe the beaker
free of sand using a kimwipe.
4. Weigh by difference a sample of sand that is approximately 0.5 g. (Note: In this
step, recall what 0.5 g of sand look like from Step 1. Use a spatula and transfer
approximately 0.5 g of sand into the weigh boat by estimating the amount
visually. You will not be using a top-loading balance.) Transfer the sand sample
into a beaker.
5. Enter your mass measurements into the datasheet.
6. When you are finished, return the sand to the bottle provided and wipe the beaker
free of sand using a kimwipe.
Datasheet:
Weighing by taring
1. Mass of weigh boat and sample
2. Mass of empty weigh boat
3. Mass of sample
______________________
0.0000 g
______________________
Weighing by difference
1. Mass of weigh boat and sample
______________________
2. Mass of emptied weigh boat
______________________
3. Mass of sample transferred
______________________
Jan 04, 2011
Page 6
Technique #5 – Use of a Bottle-Top Dispenser
Task:
1. Reach your hand into the box and draw a volume. Preset the bottle-top dispenser
to this volume.
2. Use a graduated cylinder and measure the volume dispensed by the bottle-top
dispenser. The volume collected should be within 2% of the preset volume.
3. If the volume being dispensed is outside the preset volume, adjust the dispenser
and repeat step 2.
4. Enter the preset volume and the volume dispensed in the datasheet.
Datasheet
1. Preset dispenser volume
_________________________
2. Volume dispensed by the bottle-top dispenser
Trial 1: __________________
Trial 2: __________________
Trial 3: __________________
Jan 04, 2011
Page 7
Technique #6 – Gravity Filtration
Task:
1. Set up the gravity filtration apparatus (Refer to Figure 22).
2. Prepare the filter paper (Refer to Figure 21).
3. Obtain a sample of sand/water mixture. The mixture contains soluble
contaminants.
4. Wash and filter the sand using decanting, and washing techniques.
5. Finally, transfer the washed sand to the funnel.
Space to make notes:
Jan 04, 2011
Page 8
Technique #6 – Vacuum Filtration
Task:
1. Set up the gravity filtration apparatus (Refer to Figure 22a).
2. Prepare the filter paper.
3. Obtain a sample of sand/water mixture. The mixture contains soluble
contaminants.
4. Wash and filter the sand using decanting, and washing techniques.
5. Finally, transfer the washed sand to the funnel.
Space to make notes:
Jan 04, 2011
Page 9
Technique #7 – Preparation of a Standard Solution
Task:
You will be asked to prepare a 50.00 mL standard solution of copper (II) sulfate
pentahydrate, CuSO4•5H2O.
1. Reach your hand into the box and draw a concentration. This is the concentration
of the CuSO4•5H2O standard solution you are preparing.
2. Calculate the mass of CuSO4•5H2O needed using this equation.
3. a. Concentration of CuSO4•5H2O standard solution
b. Molar mass of CuSO4•5H2O
c. Total volume of solution
d. Mass of CuSO4•5H2O to be weighed
__________________
__________________
50.00 mL
________________
4. Weigh the CuSO4•5H2O sample.
Weighing by taring
1. Mass of weigh boat and CuSO4•5H2O
2. Mass of empty weigh boat
3. Mass of CuSO4•5H2O
Jan 04, 2011
_______________________
0.0000 g
______________________
Page 10
Technique #8 – Titration
Task: Carry out an acid-base titration
1. The burette is already acclimatized with the base. Use a clean and dry beaker to
obtain a small quantity of acid.
2. Pipette 10.00 mL of the acid into an Erlenmeyer flask.
3. Add a few drops of phenolpthalein.
4. Perform an acid-base titration.
5. Repeat the titration until you are satisfied with your technique. Your titration
volume should be within 0.06 mL or less.
Datasheet for a Titration
Trial 1:
1. Final burette reading
______________________
2. Intitial burette reading
______________________
3. Volume of titrant used in titration
______________________
Trial 2:
1. Final burette reading
______________________
2. Intitial burette reading
______________________
3. Volume of titrant used in titration
______________________
Trial 3:
1. Final burette reading
______________________
2. Intitial burette reading
______________________
3. Volume of titrant used in titration
______________________
Jan 04, 2011
Page 11