2-7: Counting Atoms
1.
Start Virtual ChemLab, select Reactions and Stoichiometry, and then select Counting Atoms (3) from
the list of assignments. The lab will open in the Calorimetry laboratory.
2.
Enter the stockroom by clicking inside the Stockroom window. Once inside the stockroom, click on
the Metals cabinet and then open the first drawer by clicking on it. When you open the drawer, a Petri
dish will appear on the counter next to the cabinet. Place the sample of erbium (Er) found in the
drawer into the sample dish by double-clicking on the sample or by clicking and dragging it to the
dish. Return to the stockroom view by clicking on the green Zoom Out arrow. Place the Petri dish on
the stockroom counter by double-clicking on it or by clicking and dragging it to the counter. Click on
the Return to Lab arrow to return to the laboratory.
3.
Drag the Petri dish to the spotlight near the balance. Click on the Balance area to zoom in. Drag a
piece of weighing paper to the balance pan, Tare the balance, and then drag the erbium sample to the
balance pan and record the mass in the data and results table.
4.
Calculate the moles and the atoms of erbium and enter the results in the data and results table below.
5.
Repeat steps 2-4 for sodium, tungsten, and a metal of your choice.
Data and Results Table
erbium (Er)
Mass (grams) 26.7547 g
Molar Mass 68 g/mol
(g/mol)
Moles of each 0.3935 moles
element
Atoms of
2.37×1023
each element
sodium (Na)
2.9131 g
11 g/mol
tungsten (W) Rhenium (Re)
51.0255 g
74 g/mol
55.2706 g
75 g/mol
0.2648 moles 0.6895 moles 0.7369 moles
1.59×1023
4.15×1023
4.44×1023
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