When dealing with large quantities of something, it is often convenient to defin

Question

When dealing with large quantities of something, it is often convenient to define a term that refers to a certain quantity. For example, a dozen of anything is 12. If I buy 3 dozen doughnuts, I have purchased 3*12=36 doughnuts. In dealing with large quantities of molecules, the term mole refers to 6.022×1023 molecules. This number is referred to as Avogadro's Number.

Suppose you have 2.84 moles of a certain type of molecule. How many molecules do you have? = 1.71 x 1024

Using the idea of a dozen as an example again, if you have 2 dozen blocks and their total mass is 48 kg, the mass of one block would be 2.0 kg. Suppose you have a sample of 2.79 moles of a certain type of molecule and the total mass is 50.8 g. What is the mass of a single molecule?

Explanation / Answer

2.84 moles = 2.84 (6.022 x 1023) molecules = 2.84 (6.022 x 1023) = 1.71 x 1024

mass of single molecule = total mass /number of molecules = 50.8 / 2.79 x 6.022 x 1023 = 3.02 x 10-23

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