MathBench > Measurement

Calculating Molar Weight

easter eggsHow much does a mole weigh?

You can have a dozen eggs, and that would weigh about 12oz. A dozen donuts would weigh about 24 ounces, and a dozen cornflakes would weigh about 6 grams.

Likewise, a mol of atoms has a different weight, depending on what atom you're talking about.

If I wanted to know how much a dozen eggs weighed, I could take the average weight for one egg and multiply by 12:

1 oz * 12 = 12 oz = 1 dozen eggs

On the other hand, a dozen cans of soda would have a different weight:

12 oz * 12 = 144 oz = 1 dozen cans of soda


helium balloons That was easy. We could do the same thing with atoms -- for example, a mol of helium:

.0000000000000000000000664 g * 602,200,000,000,000,000,000,000 = ???

Two problems here:

•  How did I know how much a helium atom weighs?

•  What a nasty computation!!! Miss a few zero's and you're completely screwed. There must be an easier way...