Table of Contents

• Prequiz...
• 1: What is a mole?
• 2: How much does a mole weigh?
• 3: Molar weights made easy
• 4: ...but not quite that easy
• 5: Using the Periodic Table
• 6: Water
• 7: Practice with sulfuric acid
• 8: ...and caffeine
• 9: Going backwards
• 10: ...and rubies
• 11: Summary

How much does a mole weigh?

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

50 grams * 12 = 600 grams

 

 

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 zeros and you're completely screwed. There must be an easier way...