[javydog]

I feel like i'm lacking in some fundamental concept about maths here. I see the formula:

sample (g)/atomic weight x avogadros number

 and just cant understand why we're taking these steps and how it's ending up telling us the number of atoms. Can someone help me here? Is there a basic maths video that can help me understand? Thanks

Edit: Btw I understand what avogadros number is (the number of atoms in 12g of carbon-12) and I understand what atomic mass is (the number if grams in 1 mole of the substance) but i still just can't get something to click when I look at this!

[Borek]

This is a bit lousy formula (works only for pure elements), but do you know what is the result of the division?

Say you have 8 g of sulfur, sulfur atomic weight is 32 g/mol, what do you get when you divide [itex]\frac {8 g}{32 \frac g{mol}}[/itex]?

[javydog]

The number of moles in the sample? I think it's starting to click but can you explain how dividing that way gets us the number of moles?

[Borek]

The number of moles in the sample? I think it's starting to click but can you explain how dividing that way gets us the number of moles?

Look at units - grams cancel out.

Or think this way: you are told you need 9 glasses of water to feel a large jar. You have just three glasses of water. How many jars can you fill up? Isn't it 3/9? Same with moles when given mass of a substance and its molar mass.

Now, once you know number of moles - how do you calculate number of atoms? (or molecules, or whatever)