SCH 3U Lab: Preparation of Solutions: Creating A Liquid Rainbow
Introduction:
What do the effectiveness of a medicine, the safety of a chemical reaction, and the cost of an industrial process have in common?
They all depend on solutions that are made carefully with known concentrations. A solution with a known concentration is called a
standard solution. There are two ways to prepare an aqueous solution with a known concentration. You can make a solution by
dissolving a measured mass of pure solute in a certain volume of solution. Alternatively, you can dilute a solution of known
concentration. In this lab you will practice preparing solutions of known concentration following the proper procedure and using the
appropriate equipment. To test the accuracy of your measurements you will attempt to layer your solutions according to their density.
Materials:
Goggles and apron
Large test tube (110 mL)
25 or 50 mL Graduated cylinder
Granulated Sucrose
Sucrose stock solution – 5.84 mol/L
Distilled water
Box of food colouring
10 mL Pipette
Glass stir rod
25 mL Volumetric flask
40 and 250 mL Beaker
Retort stand and test tube clamp
Pre Lab Section:
Calculate the missing data from Tables 1 and 2. Show your calculations in your lab report. Include all units and consider significant
digits. Make sure you are working with the right units! Indicate which value you are calculating by it’s letter (eg. A) )
Table 1. Solutions 1 and 2: prepared from the stock solution
Volume of Stock
Volume of
Conc of Stock
Solution #
Solution Used
Distilled Water
Solution (mol/L)
(mL)
Added (mL)
1
5.84
A)
B)
2
5.84
15.6
C)
Table 2. Solutions 3 and 4: Prepared from solid solute
Mass of
Molar Mass of
Total Volume of
Solution #
Granulated
Sucrose (g/mol)
Solution (L)
Sucrose (g)
3
E)
342.30
0.025
4
6.25
342.30
0.025
Table 3. Rainbow Colour Scheme
Solution #
Colour
Order of Addition
1
Blue
1
2
Green
2
3
Yellow
3
4
Orange
4
5
Red
5
Total Volume of
Solution (L)
0.025
0.025
Final Conc of
Solution (mol/L)
5.11
D)
Final Conc of
Solution (mol/L)
2.19
F)
# Drops
2 drops of blue
2 drops of green
3 drops of yellow
1 red + 1 yellow
2 red
Procedure:
__ 1.
__ 2.
__ 3.
__ 4.
Place a check mark in the space provided as you complete each step of the lab
Put on your apron and safety goggles. DO NOT take them off until the end of the lab.
Use the test tube clamp to secure your test tube to the retort stand.
Prepare solution 1 from the stock solution:
a. Measure the correct volume of stock solution using a 25 mL graduated cylinder. Transfer into the 40 mL beaker.
b. Measure the correct volume of water using a 25 mL graduated cylinder. Transfer into the 40 mL beaker. (Total
volume must be 25 mL)
c. Add the food colouring, see Table 3 for the colour scheme. Stir with a glass stirring rod.
d. Carefully and slowly transfer your solution to the test tube – the slower you add the solutions to the test tube the
less the layers will mix together.
__ 5. Repeat step 5 for solution 2.
__ 6. Prepare solution 3 from the solid sucrose:
a. Obtain the required mass of sugar and transfer into a 250 mL beaker.
b. Add 25 mL of water (using a graduated cylinder) and stir.
c. Reduce the solution to about 25 mL by pouring some down the sink.
d. Add the food colouring, see Table 3 for the colour scheme. Stir with a glass stirring rod.
e. Use the pipette to SLOWLY add this layer. – the slower you add the solutions to the test tube the less the layers
will mix together. Keep the pipette low into the test tube.
__ 7. Prepare solution 4 from the solid sucrose:
a. Refer to the Preparing Solutions handout for complete steps on measuring, dissolving, transferring and diluting
the solution. Use the 25 mL volumetric flask.
b. Transfer the solution from the flask to the 40 ml beaker and add the food colouring and stir. See Table 3 for the
colour scheme.
c. Using the pipette SLOWLY transfer your solution to the test tube.
__ 8. Solution 5 is a 10 mL mixture of water and food colouring. Use the pipette to transfer 10 mL of deionized water to the 40
mL beaker. Add the food colouring according to Table 3, stir, and carefully add the solution to the test tube.
__ 9. Present your final product to the instructor to be graded.
__ 10.Divide the clean up fairly between yourself and your partner. Make sure all glassware that came into contact with a
sucrose solution is thoroughly washed. Put away all of the equipment and then return to your lab area and wipe the lab
bench with a moistened paper towel.
Analysis Questions:
1.
2.
3.
4.
What mass of sucrose was dissolved in each of the 5 solutions? Show your work
Why were the different sucrose solutions able to remain separate from one another?
Without physically mixing the layers how could you speed up the process of the layers merging together?
Like an oil and water mixture, two sucrose solutions of different concentrations will stay separate if added carefully. Why
does the oil and water remain separate after mixing but the sucrose solutions become permanently mixed?
Lab Report
1) Title block (date, name, course, appropriate specific title)
2) Purpose – Write in one or two sentences.
3) Materials and Methods – write ‘Refer to lab sheet’
4) Pre-Lab calculations
5) Analysis questions
Marking Scheme
Sections
Level 1
Minimal
requirements
are met
Level 2
Level 3
Some of the
Most of the
requirements
requirements
are met
are met
Communication
Level 4
All of the
requirements
are met
Weight
1x
Title Block
- contains an appropriate title &
date
Appropriate general purpose in
one or two sentences
Pre-Lab
All units are included, problem
solving is well organized
1x
2x
Overall Communication
/16
Inquiry
Experimental technique as
reflected by the striations of the
rainbow layers
Pre-Lab
Calculations completed correctly,
units and s.d. are included
Analysis Questions – mass of
sucrose calculated correctly with
units, s.d.
Analysis Questions – separation
of solutions, speed up mixing
process, oil and water question
Overall Inquiry
1x
4x
1x
3x
/36