# Convert grams to moles formula?

How many moles of N are in 0.203g of N2O?

 jcaron2 Posts: 983, Reputation: 1034 Senior Member #2 Jun 14, 2011, 02:00 PM
First you need to figure out how much a mole of N2O weighs. This, by definition, is called the molecular weight. You find it by adding up the atomic weights of each of the constituent atoms. For example, an N2O molecule has two N atoms. Since N has an atomic weight of 14.0067, that means that a mole of N2O molecules contains 2 x 14.0067 = 28.0134 g of N. It also contains a certain mass of oxygen which must be added in to find the molecular weight, but I'll let you look up that value.

Once you know the mass of a mole of N2O, you can figure out how many moles you have by dividing 0.203g of N2O by the molecular weight you calculated. You should find that you have a little less than 5/1000s of a mole.
 Unknown008 Posts: 8,147, Reputation: 3745 Uber Member #3 Jun 15, 2011, 11:32 AM

One slight correction in your post Josh

One mole of N2O contains 2 moles of N.

You have to multiply the answer that you get by 2 after getting it!
 jcaron2 Posts: 983, Reputation: 1034 Senior Member #4 Jun 15, 2011, 11:56 AM
Comment on Unknown008's post
Quote:
 Originally Posted by Unknown008 One slight correction in your post Josh :) One mole of N2O contains 2 moles of N. You have to multiply the answer that you get by 2 after getting it!
Isn't that what I said (more or less)? I never outright said there were two moles of N, but I did say there were two atoms per molecule so you have to multiply N's contribution by 2.
 Unknown008 Posts: 8,147, Reputation: 3745 Uber Member #5 Jun 15, 2011, 12:06 PM

Hm... I'll wait some time before getting back to it, or the actual answer will get over the place while we're trying to sort it out
 Unknown008 Posts: 8,147, Reputation: 3745 Uber Member #6 Jun 18, 2011, 12:18 PM

Okay, the OP seems unwilling to follow up.

First, we got to find the number of moles of N2O.

No. of moles of N2O = Mass/Mr = 0.203/(14+14+16) = 0.004613636 mol = 0.00461 mol

And thus number of moles of N = 2 x 0.00461 = 0.00923 mol

 jcaron2 Posts: 983, Reputation: 1034 Senior Member #7 Jun 18, 2011, 01:19 PM

Ahhh, got it.

As you've probably guessed, I misread the question. Yes, you're right. There are twice as many moles of N as there are of N2O. I read it as "how many moles of N2O".

This is why YOU are the chemistry expert, not me.

Btw, I'm still unable to rep you until I spread it around a little more.
 Unknown008 Posts: 8,147, Reputation: 3745 Uber Member #8 Jun 18, 2011, 01:31 PM

It's okay, don't worry

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