Not good with math or chemistry. Help with moles please.?

Question

How many moles are in the molecules shown.

1.5X10^20 (1.5 times 10 to the 20th power)

I've done the others by dividing with avogadro's number (6.02X10^23) but I was just winging it can't work this out.

Answer 1

k

Here's the deal with moles. A "mole" is an amount of a substance... think of it as a "dozen". You can have a "dozen" of anything--donuts, trucks, pieces of paper, whatever. In the same way, a "mole" is (instead of 12 items), 6.022x10^23 items. That's way more stars than there are in the universe, but anyway...

In order to have 1 mole of molecules, you have to have 6.022x 10^23 molecules. Since you have less than that, you know your answer should be less than 1.

1.5x10^20 / 6.022x10^23 = 2.5x10^-4.

Answer 2

to find moles, divide molecules by avogadro's number

1.5 x 10^20 / 6.02 x 10^23 = 2.5 x 10^ -3

Answer 3

Well, that is also what you do here. You might "cheat" by changing the molecules to 15 x 10^19 to make the division easier. You will wind up with an answer x 10^-4.

Answer 4

I believe you are right in the approach. One easy way to understand these calculations is by using the staircase approach. We know that 1 mole = Avogradro's # of something (atoms, molecules, ions), then you want to change units so you try to cancel them multiplying your data times your known equivalence:

Y molecules x (1 mole/# molecules per mol aka Avo's #) =

and you are done!!

Answer 5

Think of moles as your little base camp in the middle right. if you want liters you multiply by 22.4, if you want grams you multiply by atomic weight, if you want molecules, you multiply by 6.02 x 10 ^ 23. So in thoery you multiply OUT to get from moles to something else. To cancel that out, you divide IN to get from something else to moles. So if you multiply by 6.02 x 10 ^23 to get from moles to molecules, you must divide by the same to get back to moles. Make sense?

Answer 6

Im not good with math eh. sorry