A dozen elephants have a different weight than a dozen rabbits- but in each case, you have a dozen animals. Just as 12 eggs is a dozen eggs, 6. 02 10 23 eggs is a mole of eggs. 6. 02 10 23 molecules of oxygen is a mole of oxygen. Moles were defined to solve the problem of counting large numbers of molecules. You can use this as a conversion factor to turn moles into molecules. For example, H 2 O has a molecular weight of 18. 0 (16. 0 for the oxygen and 1. 0 for each hydrogen), so the mole-to-gram relation for water is 1 mole water = 18 g water If you're like most students, it's this that's confusing you. Picture it this way:
Counting the molecules individually would be completely impractical. With moles, you count the number of molecules in the sample by weighing it. Similarly, a mole of oxygen gas has a different weight than a mole of water- but in each case, you have 6. 02 10 23 molecules.
Think of moles as a chemist's dozen.
Why use moles? A mole of any substance is the molecular weight of that substance in grams. Learn to convert between moles and molecules, and moles and grams.
- Using moles to count molecules. Even if you had a way to see the individual molecules, there are just too many, even in a tiny sample.
You often want to know how many molecules you have in a sample of a substance. A mole of any substance is 6. 02 10 23 molecules of that substance. For example, to figure out how many molecules there are in 0.001 moles of water, 0.001 moles water ( 6. 02 10 23 water molecules 1 mole water ) = 6. 02 10 20 water molecules100 water molecules ( 1 mole water 6. 02 10 23 water molecules ) = 1. 66 10 -22 moles water
- Using masses to count moles. The number of grams in a mole is different from substance to substance. Chem concept paper research.