Chapter 11: The Mole
The Mole Lab

 

Introduction:

A mole is a term used to describe an amount of atoms or molecules or formula units.  This is much like when the term dozen is used to describe a certain number of eggs.  The eggs may be different colors.  The eggs may have different sizes (large, extra large, jumbo, etc.).  However, regardless of the size or color or weight of the eggs, there are always 12 eggs in a dozen.  In the case of atoms or molecules or formula units, there are always 602,000,000,000,000,000,000,000 or 6.02 x 1023 particles in a mole.

The numeric value for the atomic mass on a periodic table also represents the molar mass of each element.  For example, the atomic mass of carbon is 12.00 so one mole of carbon atoms (6.02 x 1023 carbon atoms) has a mass of 12.00 grams.

However, to put this into some perspective, what if you had one mole of jumbo eggs?   What would that mass be in grams?  If 1 jumbo egg has a mass of 3 ounces, then 1 mole of eggs would have a mass of about 2,000,000,000,000,000,000,000 tons!  (That's 99% of the weight of the ENTIRE solar system!)  And yet, 1 mole of carbon atoms has a mass of 12 grams! 

So, WHY do we use a mole in chemistry?  Well, since atoms (or molecules or formula units) are so ridiculously small, we have to have some useful way of making measurements in the lab.  We cannot measure the mass of individual atoms in the lab but we can measure the mass of a mole of atoms in the lab.  That is what you are going to do in this experiment.

Purpose:

The purpose of this lab is for you to discover the identity of the element at each lab station by comparing the measured mass of one mole of an element sample to the molar masses in the periodic table.  Although each station represents one mole of an element, and thus holds the same number of atoms, the molar mass of each sample is different.  In this activity, you will determine the molar mass and identify the element at each of the 12 lab stations.

Procedure:

1. Go to your assigned station.  This is a rotational lab and you will move to the next station in 3 minutes.

2. On the proper line for the station where you are now, copy the mass of the empty container to the data table later in this document.  The lab station number and the mass of the empty container is written on the bottom of the vial.

3. Use a balance to find the total mass of the container, its cap and its contents.  Record the total mass in your data table to the nearest 0.01 g.

4. Write a brief description of the physical appearance of the element onto your data table.  You will be GRADED on this section!

5. When the time is called, go to the next station higher in number compared to the one where you start.  Repeat until all 12 stations have been visited.

6. Now, calculate the NET mass of each sample and record it onto your data table.  Subtract the weight of the container from the mass total you measured for each vial.  This amount should then be recorded onto your data table.  This will be the mass of 1.0 mole of the substance within.

7. On your periodic table, located the element which has the atomic mass equal (or closest to) the calculated mass of each sample.  Write the symbol and the atomic mass from the periodic table onto your data table.  You will be GRADED on this section!

  • NOTE: If some of the values you calculated are "close" but NOT exact, you will need to refer to your observations to see if you can determine which element you have.  In fact, you may need to actually look up on an interactive periodic table some of the physical characteristics so that you can correctly identify your element.

Data Table:  Print off here.

 

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