Maulik Masaliya
Experiment 7: How much is a mole? “Avogadro’s number Dilemma”
October 11, 2020.
Summary:
In this experiment we will learn more about moles, amu and Avogadro’s number and try to
estimate estimate is using the samples provided. We will form a monolayer of stearic acid
molecules on the surface of water and based on the amount of stearic acid required to cover the
surface of water and the given cross-sectional area of a stearic acid molecule we will calculate
Avogadro’s number.
Introduction:
A mole is a standard scientific unit for measuring large quantities of very small entities such as
atoms, molecules or other specified particles. The mole was previously defined as the number of
atoms determined experimentally to be found in 12 grams of C-12. The number of units in a
mole also bears the name Avogadro’s number. The Avogadro’s number is the number of
molecules in a mole of a substance. The value of this number equals to 6.022 x 1023. We will
try to estimate this number by forming a monolayer of stearic acid molecules on the surface of
water. Based on the amount of stearic acid necessary to cover the surface and the given
information, we can calculate the Avogadro’s number.
Materials:
1. 50 mL beaker
2. Soap
3. Tap water
4. Acetone
5. Distilled water
6. Hexane/Stearic Acid
7. Pasteur pipet
8. Watch glass
9. Ruler
10. Laptop
11. Lab manual
12. Calculator
Focus questions:
1. What is Avogadro’s number based on your measurements?
Based on our measurements, the Avogadro’s number is 5.7 * 1023 molecules/mol.
2. How does your experimental value compare to the actual value and the class average?
The class average was 5.7 * 1023 and the actual is 6.022 * 1023. The difference is
due to a 5% error in the experiment.
3. How accurate is the data from your peers from last years?
We do not have the data from our peers last year experiments.
4. How precise is it?
We do not have the data from our peers last year experiments.
, Experiment/ Observation:
Part 1:
Trial Drops per 3mL Volume of each drop. (mL)
1 190 0.0157
2 185 0.0160
3 195 0.0154
Part 2:
Trial Drops
1 20
2 25
3 30