Mole Determination

Theory Atoms are the smallest whole units of matter. In the world of chemistry, chemists are interested in the number of atoms or molecules involved in reactions. However, because atoms and molecules are so small, they rely on Avogadro’s number (6.02 X 1023) to count atoms and/or molecules. This large number represents one mole of substance. For example, if you have one dozen of CDs, you possess 12 CDs. If you have one mole of CDs, you possess 6.02 X 1023 CDs (what a music collection!). Therefore, the term mole is used to represent a specific quantity. And, because atoms are so small, one mole represents a very large number.

Purpose To use moles, atoms, and grams in a variety of mathematical conversions.

Safety Fortunately, there are no significant risks in this lab. However, to continue to build good habits, you will be expected to wear safety goggles and closed-toed shoes.

Procedures

Part A - Aluminum Foil 1. Obtain a square piece of Al foil approximately 12 cm x 12 cm. 2. Measure and record the exact length and width of your piece of Al foil to the nearest 0.1 cm. 3. Fin the mass of your Al foil. Return the foil to its proper place.

*Note: The Density of Al is 2.70 g/mL (1 mL = 1 cm3)

Part B - Samples of Elements and Compounds 1. At each electronic balance, you will find small vials containing samples of either an element or a compound. 2. Determine and record the name of the element or compound, the appearance, and the mass of the vial and element/compound. 3. After you have completed step #2 for all of the vials at your electronic balance, rotate to the next balance and repeat steps #2 and #3.

**Pre-Lab: Go to WebAssign and complete assignment Data Tables

Part A - Aluminum Foil

Density of Aluminum (g Length of Aluminum foil (cm) Width of Aluminum foil (cm) Mass of Al Volume of foil (cm3) Height of Al foil (cm) Moles of Al in foil Atoms of Al in foil Atoms thick of Al foil

Part B - Samples of Elements and Compounds

See Attached Calculations

Part A - Aluminum Foil 1. Use the density of aluminum and the mass of the aluminum foil to find the volume (in cm3). 2. Find the thickness (in cm) of the foil knowing that volume = L x W x H 3. One Al atom is 2.5 X 10-8 cm in height. Calculate the thickness of the Al foil in atoms. 4. Find the moles of Al present in your piece of foil 5. Find the total number of Al atoms in your foil.

Part B - Samples of Elements and Compounds 1. Determine the mass (grams) of the element or compound within each vial. 2. Calculate the molecular mass (for compounds) or atomic mass (for elements). 3. Convert mass (grams) to moles using the molecular/atomic masses. 4. Convert moles to atoms (for elements) or molecules (compounds).

Questions 1. In order to convert grams to moles for any element or compound, what must be used? 2. In order to convert moles to atoms or molecules, what number must be used? 3. How many steps are necessary to convert from grams to atoms/molecules or vice versa? 4. Create a grams to moles conversion problem. 5. Create a moles to atoms or molecules conversion problem. 6. Create a grams to atoms or molecules conversion problem.

References Adapted from a lab created by Elizabeth Helfant and Chris Sellers