Experiment Estimating Avogadro Number Lab Report

Videos Shows doing drop for 1 mL, length of water surface and drops to form monolayer https://www.youtube.com/watch?v=TlPkKVAj028
Shows just doing drops for Monolayer

Watch this video and respond the question below.

How long it takes the oil to create the expanded layer that calms the waves?

A couple of minutes

1 minute

10 minutes

A couple of seconds

Question 2

How thick was the layer of oil created?

One molecule thick

Thousands of molecules thick

A table spoon

Oil doesn’t form a layer

Question 3

What application of the monolayer is explained in the video?

Better frying pans

Invisible glass for phones

Invisible clothing

Walking on water

Question 4

What is the name of the acid we will use to create a monolayer in experiment 7?

Stearic acid

Oleic Acid

Sulphonic acids

Acetic acid

Question 5

The _____________ head group will stay near the water and the ______________ tail will orient themselves away from the water. Chck fig 7.2

insoluble, miscible

polar, soluble

Non-polar, polar

polar, non-polar

Question 6

Why do you calibrate a dropping pipet in part 1?

To determine the number of drops in 1 mL

To clean the pipet

To count the number of molecules on hexane

To learn how to use a pipet

Question 7

Once we place the watch glass on a beaker; we will fill the the watch glass to the brim with ____________________.

tap water

hexane

distilled water.

salt water

Question 82 pts

Watch this video to have a visual reference of how to create a monolayer of stearic acid. Pay attention to the lens or globule shape in the surface formed that indicates the monolayer is complete.

The number of drops needed will depend on your pipet and the size of your watch glass. Is it important to count the exact number of drops?

No, We don’t need to know the volume.

Absolutely. We need the number of drops for our calculations. The number of drop will allow us to calculate the volume (ml) needed to form the monolayer.

Question 9

Drops of hexane/mL 19 drops/mL
Number of drops stearic acid/hexane used for monolayer 3 drops
Diameter of water surface 7.2 cm
Concentration of stearic acid/hexane 0.10 g/L
Molar Mass of stearic acid: 284 g/mol
Density of stearic acid 0.870 g/mL

Calculate the volume of stearic acid/hexane in the monolayer.

15 ml

150.78994 ml

0.157894737 mL

40.71504079 ml

Top of Form

Question 10

Pre-Lab

What is the value of Avogadro’s number?

6.022 * 1012

6.022 * 1023

None of the above

6.220 * 1023

6.012 * 1023

Question 11

Pre-Lab

In this lab, we created a layer of stearic acid one molecule thick on the surface of a watch glass filled with water. The              [“”, “”]            head group will stay hear the water and the              [“”, “”]            will orient themselves away from the water.

Question 12

Pre-Lab

For waste, organic solutions, like hexane, should be placed in the              [“”, “”]            waste.

Question 13

Pre-Lab

Remember, please round at the end of the calculation.

1. Calculate the volume of stearic acid/hexane in the monolayer:

N u m b e r o f d r o p s ⋅ 1 m L s o l u t i o n 19 d r o p s

[“”, “”, “”, “”, “”]

1. Calculate the mass of stearic acid in the monolayer (using answer to #1 above as volume):

v o l u m e i n m L ⋅ 1 L 1000 m L ⋅ 0.10 g 1 L =

[“”, “”, “”, “”, “”]

1. Calculate the volume of stearic acid in the monolayer in mL (using answer to #2 above as mass):

m a s s i n g ⋅ ( 1 m L 0.870 g ) =

[“”, “”, “”, “”, “”]

1. Calculate the thickness of the monolayer in cm (using answer to #3 above as volume):

first, find area, A = π r 2

second, find thickness, t = v o l u m e a r e a = a n s w e r t o 3 a r e a

[“”, “”, “”, “”, “”]

1. Calculate the volume of a stearic acid molecule in the monolayer (using answer to #4 above as thickness, t):

V o l u m e = l ⋅ w ⋅ h = ( 1 5.44 ) ⋅ ( 1 5.44 ) ⋅ t = t 3 ( 5.44 ) 2 =

[“”, “”, “”, “”, “”]

1. Calculate the number of stearic acid molecules in the surface layer (using answer to #3 above as volume of stearic acid as monolayer and answer to #5 as volume of stearic acid molecule):

v o l u m e o f s t e a r i c a c i d m o n o l a y e r ⋅ ( 1 c m 3 1 m L ) ⋅ ( 1 m o l e c u l e v o l u m e o f s t e a r i c a c i d m o l e c u l e ) =

[“”, “”, “”, “”, “”]

1. Calculate the number of moles of stearic acid in the surface layer (using answer to #2 above as mass):

m a s s o f s t e a r i c a c i d ⋅ ( 1 m o l 284 g ) =

[“”, “”, “”, “”, “”, “”]

1. Calculate the value of Avogadro’s number (using answer to #6 above as molecules and answer to #7 above as moles):

m o l e c u l e s o f s t e a r i c a c i d m o l e s o f s t e a r i c a c i d =

[“”, “”, “”, “”, “”]

Question 14

Data

Part 1

 Trial 1 Trial 2 Trial 3 Drops of Hexane # drops # drops # drops Average drops [b1]

Please type a numerical number in for the average # of drops, without units.

Question 15

Data

Part 1

Why is it important to do the calibration of the dropper quickly?

Stearic acid sublimes quickly

Stearic acid evaporates quickly

Stearic acid is viscous

None of the above

Question 16

Data

Part 2

Please type a numerical number in for the average # of drops of solution used for the monolayer, without units.

Question 17

Data

For Trial #1 data, Calculate Avogadro’s number using the same series of calculations.

Remember, please round at the end of the calculation.

1. Calculate the volume of stearic acid/hexane in the monolayer:

N u m b e r o f d r o p s ⋅ 1 m L s o l u t i o n 19 d r o p s

1. Calculate the mass of stearic acid in the monolayer (using answer to #1 above as volume):

v o l u m e i n m L ⋅ 1 L 1000 m L ⋅ 0.10 g 1 L =

1. Calculate the volume of stearic acid in the monolayer in mL (using answer to #2 above as mass):

m a s s i n g ⋅ ( 1 m L 0.870 g ) =

1. Calculate the thickness of the monolayer in cm (using answer to #3 above as volume):

first, find area, A = π r 2

second, find thickness, t = v o l u m e a r e a = a n s w e r t o 3 a r e a

1. Calculate the volume of a stearic acid molecule in the monolayer (using answer to #4 above as thickness, t):

V o l u m e = l ⋅ w ⋅ h = ( 1 5.44 ) ⋅ ( 1 5.44 ) ⋅ t = t 3 ( 5.44 ) 2 =

1. Calculate the number of stearic acid molecules in the surface layer (using answer to #3 above as volume of stearic acid as monolayer and answer to #5 as volume of stearic acid molecule):

v o l u m e o f s t e a r i c a c i d m o n o l a y e r ⋅ ( 1 c m 3 1 m L ) ⋅ ( 1 m o l e c u l e v o l u m e o f s t e a r i c a c i d m o l e c u l e ) =

1. Calculate the number of moles of stearic acid in the surface layer (using answer to #2 above as mass):

m a s s o f s t e a r i c a c i d ⋅ ( 1 m o l 284 g ) =

1. Calculate the value of Avogadro’s number (using answer to #6 above as molecules and answer to #7 above as moles):

m o l e c u l e s o f s t e a r i c a c i d m o l e s o f s t e a r i c a c i d =

What did you get for Avogadro’s number?

Please type in the first portion only: __________ x 1023

(If your number is 2.2 x 1022, then convert this to 1023, which is 0.22 x 1023, and you would type in 0.22.

Question 18

Post-Lab

What is the mass of 5.47 mole of stearic acid? (MW = 284 g/mol)

Question 19

Post-Lab

The density of stearic acid is 0.870 g/mL. What is the volume of 7.8 x 10-6 mole of stearic acid?

Question 20

Post-Lab

What assumptions were made in this experiment to arrive at a value for Avogadro’s number?

Stearic acid is just non-polar

Stearic acid molecule is rectangular in shape

Stearic acid is just polar

Stearic acid has a polar and non-polar end

Question 21

Post-Lab

What is the mass, in grams, of one molecule of stearic acid have?

Please type in the: __________ x 1022 g

Question 22

Post-Lab

Regarding the graph, answer the questions below:

Calculate the slope of the line. Remember to use points off of the line not data points and include units.

Please type in the: __________ x 1023 molecules/mol

Question 23

Post-Lab

Regarding the graph, answer the questions below:

Can the value of the y-intercept, b, be read directly from the graph above?

yes

no

Question 24

Post-Lab

Regarding the graph, answer the questions below:

What is the y-intercept?

Please type in the: __________ x 1015 molecules

Question 25

Post-Lab

Regarding the graph, answer the questions below:

Write the equation for the line in the form Z = mn + b

Z = (1.6*1015  molecules/mol)n + 6.09 * 1023molecules

Z = (6.09 * 1023 molecules/mol)n + 1.6*1015 molecules

Question 26

Post-Lab

Please visit molview.org (Links to an external site.) and type in “stearic acid” in the search bar (magnifying glass,. upper left hand corner)

What color ball is carbon in the ball and stick model?              [“”, “”, “”]

What color ball is hydrogen in the ball and stick model?              [“”, “”, “”]

What color ball is oxygen in the ball and stick model?              [“”, “”, “”]

What kind of bonds are between carbon and carbon in stearic acid?              [“”, “”, “”]

What kind of bonds are between carbon and hydrogen in stearic acid?              [“”, “”, “”]

What kind of bonds are between carbon and oxygen in stearic acid?              [“”, “”, “”]

What kind of bonds are between oxygen and hydrogen in stearic acid?              [“”, “”, “”]

How many carbon atoms are in stearic acid?              [“”, “”, “”, “”]

How many oxygen atoms are in stearic acid?              [“”, “”, “”, “”]

How many hydrogen atoms are in stearic acid?              [“”, “”, “”, “”]