Chemical Quantities - The Mole.

Chalk, Penny, Sugar Cube Lab, and Aluminum Foil Thickness Lab, and Empirical Formula of a Compound Lab

Chalk, Penny, and Sugar Cube Lab

Part 1: You will be given a pre-1982 penny, a piece of chalk, and a sugar cube. You are to find the number of representative particles in each item. If you feel you need more information, you need to ask me. For this part, write your own procedure, data table, and show your calculations.

Part 2: After you have found the number of particles in the chalk, write your answer on the board. Now find the number of particles of chalk you left on the board. Write your procedure, data, and show your calculations.

Part 3: Calculate the percent uncertainty in your penny value from part 1.

No other parts of a write-up are needed.

Aluminum Foil Thickness Lab

How thick is aluminum foil in centimeters? How many atoms thick is this? The small size of any one atom gives a clue to the relatively large number of atoms in a sample of matter that we can pick up and measure. The size of an aluminum atom was measured by a process called x-ray diffraction and found to be about 2.5 x 10-8 cm long. The purpose of this activity is to relate the size of an aluminum atom to the thickness of a piece of aluminum foil.

In order to find the thickness in terms of atoms you will need to know the density of aluminum, 2.70g/cm3, and compute the thickness of your piece of foil. Before you come into lab write a short introduction, hypothesis (how many atoms thick do you think a piece of Al foil is and why), copy the procedure below, write a data table, then copy the calculations table.

Procedure:

  1. Obtain a square piece of Al foil approximately 12 cm x 12 cm.
  2. Measure and record the length and width of the foil to the nearest 0.1 cm.
  3. Find the mass of the foil. Return the foil to the proper place.
Data Analysis:
Calculations:
For the calculations, copy the table below. Show your work for calculations and record the answers in the table.
  1. Density of Al _________
  2. Mass of Al foil _________
  3. Volume of foil (cm3) _________
  4. Height of foil (cm) _________
  5. Atoms thick of the foil _________
  6. Moles of Al in foil _________
  7. Atoms of Al in foil _________
C. Use the density and the mass to find the volume.
D. To find the thickness (H), you know that V= L x W x H. Using other information in your data table, find H.
E. One aluminum atom is 2.5 x 10-8 cm thick. Find the thickness in atoms using the height.
F. Knowing the mass of your foil, find the moles of Al.
G. Knowing the moles of Al, find the total number of atoms in the foil.

Question:
 If the population of the world is 5.6 x 109 individuals, how many atoms of aluminum could you distribute to each person from your sample of aluminum foil?
Evaluation: As usual.
Conclusion: As usual.

Empirical Formula of a Compound Lab

In this lab you will determine the empirical formula of the compound magnesium oxide. The compound will be made by burning magnesium ribbon in air.

Before you come into lab:

  1. Write an introduction/background. Be thorough and follow everything from the lab writeup handout. When you discuss the problem to be investigated, be sure to state what information will be needed in order to determine the empirical formula. Also include any definitions you may think are relevant. This should be written in paragraph form in complete sentences.
  2. Write a hypothesis.
  3. Write the materials and procedure in your own words (or copy mine).
  4. Make up a data table.
Materials:
ring stand, ring, clay triangle, Bunsen burner, crucible with lid, tongs, magnesium ribbon, balance, goggles.

Procedure:

  1. Set up the ring stand with the ring. Place the clay triangle on the ring. Place the burner under the clay triangle.
  2. Clean a crucible and lid with water. Heat them to dry, then continue heating for 5 minutes. Allow to cool for 5 minutes. For the rest of the lab, use the tongs to handle the crucible, do not touch with your hands.
  3. Mass the crucible and lid. Record.
  4. Place a coiled 25 cm length of magnesium ribbon in the crucible. Mass the crucible, lid, and Mg. Record.
  5. Do not look directly at the magnesium burning. Over a high flame, heat the uncovered crucible until the magnesium ignites. As soon as it is burning, place the cover over the crucible and remove the burner.
  6. After smoke production has ceased, replace the burner and continue heating the crucible. Every 2-3 minutes, carefully lift the lid and check the reaction. After heating a total of 10 minutes, check to see that the reaction is complete. The magnesium should be completely converted to a white/light grey powder. If ribbonlike material remains, continue heating until it is gone.
  7. Turn off the burner. Allow the crucible to cool completely (at least 7 minutes).
  8. Mass the crucible, lid and magnesium oxide. Record.
  9. The solid can be disposed of in the trash. Wash out the crucible and put away the materials.
Notes on the procedure: If the crucible lid is not put on right away when the magnesium starts to smoke, product can be lost. Also, if a green-yellow solid is forming, too high of a temperature is being used and magnesium nitride may be forming.

Data Analysis:
Calculate the empirical formula for magnesium oxide using your data. Show all work clearly.

Evaluation: as usual.
Conclusion: as usual.



Return to the Chem homepage.