Initial lab: avogradro and all that  (Page 4/4)

When you have completed all of your measurements, rinse your syringe with pure hexane, and dispose of all the hexane-containing solutions in the waste collection bottle provided.

Calculation Of Avogadro's Number

The calculation proceeds in several steps.

• We calculate the volume of stearic acid solution in hexane required to deliver enough stearic acid to form a monolayer.
• All of the hexane evaporates, leaving only the thin monolayer film of stearic acid, so we next calculate the actual mass of pure stearic acid in the monolayer.
• We calculate the thickness of the stearic acid monolayer, using the known density of stearic acid and the area of the monolayer.
• Assuming the stearic acid molecules are stacked on end and are tightly packed, and knowing that there are 18 carbon atoms linked together in the stearic acid molecule, calculate the diameter and volume of a carbon atom.
• Calculate the volume of a mole of carbon atoms in diamond; divide the molar volume of carbon (diamond) by the volume of a single carbon atom to obtain an estimate of Avogadro's number. Remember that the units of Avogadro’s number are mol-1, so you can use unit analysis to check your answer.

Initial Lab: Avogadro and All ThatReport 1

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’ work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’ work (including your laboratory partner) or misrepresent your own data (see honor code).

Demonstrations:

Balloons:

• Oxygen

• Hydrogen
• Mixture of Hydrogen and Oxygen with relevant equation: $H_2{\text{+ O}}_2\to$

Thermite:

Include description and relevant equation: ${\text{Fe}}_2{\text{O}}_3\text{+ Al}\to$

Dry Ice and Magnesium:

Include description and relevant equation: $\text{MgO + C}\to$

1. Identification of Apparatus

• beaker 

• erlenmeyer flask 

• graduated (measuring) cylinder 

• pipette  

• burette  

• Bunsen burner 

• test tube  
• watch glass

  2. Balance Use

• Mass of weighing paper and solid, ________ g
• Mass of weighing paper, __________ g
• Mass of solid, ___________g
• Mass of solid on tared weighing paper ____________g

 3. Measuring the volume of a liquid

• Mass of 50 mL beaker and water, g ______________
• Mass of 50 mL beaker, g ______________________
• Mass of water from graduated cylinder, g___________
• Mass of 50 mL beaker and water, g ______________
• Mass of 50 mL beaker, g ______________________
• Mass of water from pipette, g ____________________
• Mass of 50 mL beaker and water, g ______________
• Mass of 50 mL beaker, g ______________________
• Mass of water from burette, g ____________________

From a consideration of the masses of water measured above, and given that the density of water is 1 g/mL, decide on an order of which is the most accurate method of volume measurement – measuring cylinder, pipette, or burette with (1) being the most accurate?

(1)

(2)

(3)

How precisely could each of the apparatus used be read?

(1) measuring cylinder

(2) pipette

(3) burette

 4. Estimation of Avogadro's Number

Measurement of the volume of stearic acid solution required to cover the water surface

Calculation Of Avogadro's Number

a. Calculation of the thickness of a monolayer of stearic acid

b. Estimation of the size and volume of a carbon atom

c. Calculation of the volume of a mole of carbon atoms

d. Calculation of the volume of a mole of carbon (diamond) volume of a single carbon atom (Avogadro's number)