Dilutions & Solutions
Proper use of Pipets, Burets, and Volumetric Flasks
Introduction
In this lab the student will use various types of measuring glassware to make different strength
solutions of Copper II Sulfate. The strengths will be checked by measuring the absorbance of
the solutions on a spectrophotometer. Proper pipeting and bureting procedures, as outlined in the
Chemical Technicians Ready Reference Handbook, will be utilized throughout.
Materials
Copper II Sulfate Pentahydrate [CuSO4•5H2O], D.I.W., triple beam scales, spatula,
glassware (stirring rod, beakers, burets, volumetric pipets, volumetric flasks)
A. Mixing of the Primary Standard - (Volumetric Flasks)

Weigh out 2.00g CuSO4•5H2O; use a weighboat & triple beam scales.

Transfer the powder to a 100mL beaker, rinsing the weighboat into the beaker assuring
that no chemical is left behind. Use deionized distilled water (DIW) at all times when
mixing reagents today.

Add some DIW to the beaker to dissolve the Copper II Sulfate. Do not use more than
~60mL.

Transfer the dissolved Copper II Sulfate to a 100mL flask. Rinse the beaker into the
flask. Add water to the mark, placing the meniscus on the line.

Stopper the top of the flask and shake well. Do not use your finger as a stopper! This is
Solution #1, the Primary Standard, label it.

Take Solution #1 to the spectrophotometer and read its absorbance at 810nm. Remember
to blank the spec. Record this abosrbance on the data sheet. The absorbance should be
between 0.910 and 0.980, if it is not, check with the Instructor.
You may do Part B or Part C next.
B. Serial Dilutions (Pipets)

Using a clean 1mL volumetric pipet, transfer 1.0mL from your Primary Standard to a
clean 100mL volumetric flask. Add water to the mark, stopper, and shake well. This is
Solution #2, label it.

Using a clean 10mL volumetric pipet transfer 10.0mL from your Primary Standard to a
clean 100mL volumetric flask. Add water to the mark, stopper, and shake well. This is
Solution #3, label it.

Using a clean 10mL volumetric pipet transfer 10.0mL from Solution #3 to a clean
100mL volumetric flask. Add water to the mark, stopper, and shake well. This is
Solution #4, label it.

Measure the absorbances of Solutions #3, #4, & #2 at 810nm. Record them on your data
sheet.
note: Solutions #2, #3, & #4 are serial dilutions of the Primary Standard; #2 & #4 are of the
same concentration and should have the same absorbance.
C. Mixing Dilutions (Burets)

Set up two 50mL burets on a ringstand using a buret clamp.

Rinse and then fill one buret with your Primary Standard. Fill the stopcock by draining
some fluid through it to a waste beaker,. Refill the buret as needed and drain to the zero
mark.

Rinse and then fill the other buret with DIW. Drain to fill the stopcock & refill to zero.

In separate 50mL beakers make 20mL quantities of the below dilutions obtaining the
indicated volumes of Primary Standard and DIW from the burets.
Dilution
(% concentration)
mLs of
Primary Standard
mLs of
DIW
0%
25%
50%
75%
100%
0
5
10
15
20
20
15
10
5
0
note: swirl each beaker
to mix the solution.
5. Transfer the dilutions to cuvets. Measure and record the absorbances of these dilutions at
810nm.
6. Use the below formula to calculate the relative concentrations of your solutions. Record
these values next to their absorbances. Remix, reread, recalculate and rerecord any that are
more than 10% off from their designated strengths (column 1 in the above table).
relative % Conc. = [(ABSdilution)(100)] / ABS100%
Dilutions & Solutions
Use of Pipets, Burets, and Volumetric Flasks
Name: ___________________________
Section: ________________
Part A: Mixing of the Primary Standard (Volumetric Flasks)
Absorbance of your Primary Standard (Solution #1) _______________
Part B: Serial Dilutions (Pipets)
Absorbance of [note order]
Solution #3: _______________
Solution #4: _______________
Solution #2: _______________
Part C: Mixing Dilutions (Burets)
Absorbance of :
Dilution:
0%
___________
Relative %:
___________
25%
___________
___________
50%
___________
___________
75%
___________
___________
100%
___________
___________