[SimoneMeyer]

I know how to calculate the amount of atoms if I am given the amount of grams of the element at hand. Here is an example:
How many atoms are in 22 grams of sulfur?

But in the question that I have been presented, the only information I have is the following:
Calculate the amount of atoms in 0.250 moles of sulfur.

How do I go about doing this, does anyone have a step by step example and formula?

[Borek]

How many atoms in one mole?

What is mole definition?

What is Avogadro constant?

[SimoneMeyer]

There are 6.0221415 x 10²³ atoms per one mole.

A mole is a unit and the Avagadro constant is 6.022 141 79(30) × 10 ²³

Sorry, but I still don't understand. What formula do I use?

[MrTeo]

A mole is a unit

I think there's something more to say about that: what's the complete definition of mole?

[SimoneMeyer]

A unit of amount of a substance. Used to measure quantity?

[MrTeo]

But knowing this doesn't allow us to measure a mole of substance... You have to remember that a mole always contains an Avogadro constant of atoms, molecules, ions... depending on what kind of mole we're talking about...

Have a look at this:
http://simple.wikipedia.org/wiki/Mole_(unit)

[Borek]

There are 6.0221415 x 10²³ atoms per one mole.

Per half mole?

Per 1/4 of the mole?

Per 0.2 mole?

[SimoneMeyer]

So, 6.0221415 x 1023 divided by 4?

That's all?

If so, and even if not so, thank you so much!

[SimoneMeyer]

So, would that mean that it could have even of been carbon, and if they used the number 0.250 the answer would be the same for carbon as it is for sulfur?

[Borek]

Do you ask if 0.25 mole of carbon has the same number of atoms that 0.25 mole of sulfur? Then the answer is yes. Also 0.25 mole of silver has the same number of atoms and so on.

Note, that 0.25 mole of oxygen won't have the same number of atoms (hint: what is formula of atmospheric oxygen?)

Nitpickers will tell you that I am wrong about sulfur. Ignore them for now

Remember, you were given mass of the substance - so you have to find number of moles first.

[DrCMS]

Sulphur has got to be the worst possible element to use for this kind of question.

[SimoneMeyer]

So, the are 1.505535375 x 10 ²³ atoms in 0.250 mole of sulfur?

Is it the same if you are looking for molecules, just replace "atoms" with "molecules" ?

[Borek]

Sulphur has got to be the worst possible element to use for this kind of question.

For 0.25 mole - yes, for 22 g - no.

So, the are 1.505535375 x 10 ²³ atoms in 0.250 mole of sulfur?

Watch your siginificant digits, but yes.

If it is right... Depends. As DrCMS stated, this is bad selection of element. Elemental sulfur contains ring shaped sulfur molecules S₈, but this fact is usually ignored. So, if you ignroe this fact - your answer is correct. If you don't ignore this fact - there will be 8 times more atoms than you have calculated. What you have to do is to read mind of your teacher and to guess what s/he expects.

Is it the same if you are looking for molecules, just replace "atoms" with "molecules" ?

See earlier post by MrTeo.

[DrCMS]

Sulphur has more than 10 allotrope's as far as I remember from S₆ to S₂₀.

[SimoneMeyer]

Thank you all so much, it's greatly appreciated.