# Homework Help: Help Moles in Phosphorus?

1. Nov 7, 2009

### sunnygirl37

Help!! Moles in Phosphorus?

I have a couple problems I can't figure out.

1. How many moles of phosphorus are present in 80.1g of phosphorus?
a. 0.387 mol
b. 2.59 mol
c. 2.48 x 10(3rd power) mol
d. 15.58 x 10 (23rd power) mol
e. none of these

2. How many atoms of fluorine are there in 4.4 mol F(subscript 2)?
a. 2.6 x 10 (24th power) atoms
b. 13.2 x 10 (23rd power) atoms
c. 5.3 x 10 (24th power) atoms
d. 14.6 x 10 (-24th power) atoms
e. 0.7 x 10 (23rd power) atoms.

Any help is greatly appreciated!!

2. Nov 7, 2009

### ordirules

Re: Help!! Moles in Phosphorus?

This is a chemistry question, but anyway, if you look up on your periodic table, there is a number called the "molecular weight". For phosphorus, you should find its molecular weight is 30.974 grams/mol.
You should be able to figure out what to do from there.

Now, if you remember what a mole is, it's a weird number. It means Avogadro's number (6*10^(23)) of whatever it is you're counting. For example, if you're talking about a mole of cars, you mean Avogadro's number of cars, so 4.4 moles of Fluorine would be how many numbers of Fluorine molecules?

I hope this helps!

3. Nov 7, 2009

### sunnygirl37

Re: Help!! Moles in Phosphorus?

So I'm thinking that I would multiply the molecular weight of phosphorus (30.974) x 4.4? I got 135.2856. I'm just not sure what to do from there!?!

4. Nov 7, 2009

### ordirules

Re: Help!! Moles in Phosphorus?

First of all, those problems are not related to each other, they're separate questions, I think you're mixing them up and confusing stuff together.

Problem 1 is a very simple idea. Remember, the molecular weight is grams/mole. If the molecular weight of Phosphorus is 30.974 grams of Phosphorus per mole, that means:
for 1 mole of Phosphorus, you will get 30.974 grams of Phosphorus.

You can reverse this idea around because your equation is:
1 mole of Phosphorus = 30.974 grams Phosphorus
so 1 gram Phosphorus = 1/(30.974) moles of Phosphorus.
(this is called unit conversions, you should really review this because you can't do Chemistry without it, nor physics)

So if you have 80.1 grams of Phosphorus, how many moles of Phosphorus will you get?

For question 2:
You need to know what a mole means. I have already explained it, but i'll try again:
1 mole of (something) = 6.022 * 10^23 (something)'s

where (something) can be anything (Fluorine, Phosphorus, carbon, billiard balls)

good luck