Experiment 12: Avogadro's Number

CHEMISTRY I

Experiment 12: Avogadro's number (hand out)

Introduction:

The objective of this experiment is to determine the value of Avogadro's number and the mole concept via the use of the monolayer experiment.

Experimental data sheet: Attached

Calculations:

1. Area of monolayer

A= 3.14(8.58 cm)І / 4

A= 231 cmІ / 4

A = 57.8 cmІ

2. Molecules of stearic acid in monolayer

57.8 cmІ x 1molecule = 2.8 x 1016 molecules

2.1 x 10-15 cmІ

3. Moles of stearic acid in monolayer

Average drops of stearic acid to make up the monolayer = 6

Average drops of stearic solution in 1 mL = 96

ml of stearic acid in monolayer = 6 / 96 = .0625 ml

Grams of stearic acid in monolayer = .1ml x 1.4 x 10 -4 g ml = 1.4 x 10 -5 g

1.4 x 10 -5 gram stearic acid x 1mol stearic acid = 4.9 x10-8 mol stearic acid

284 g stearic acid

Avogadro's number = 2.8 x1016 molecules = 5.7 x 10 23 molecules/moles

4.9 x 10 -8 mol

Analysis/Discussion:

Conclusion:

POST QUESTIONS:

1. A. Volume of drops in exactly 1 ml of graduated cylinder.

B. Diameter of water on petri plate.

C. number of drops to make monolayer.

The number of drops to make 1 ml of stearic acid in graduating cylinder was different after 3 trials,

since there is already a 1% error, more trials would yield a lower percent error. Also not reading

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