Dealing with Diatomic Elements

[Ryan Agcaoili 2E]

For one of my problems in discussion, we were tasked to find the molecular formula of caffeine, which included the elements CO2, H2O, and nitrogen. I know that nitrogen exists as a diatomic element, so it is written as N2. But when I am finding the moles of nitrogen, do I treat it as N2 or N?
All responses are welcome!

[Nina Ellefsen 2D]

I would just use N

[SophiaNguyen_2L]

Since it gives you the mass in N2, you can use that value to find the mols of N2 and then just use stoichiometry to convert the mols of N2 to N. I think it'd be easier to use the mols of N to find the empirical formula of caffeine.

[Kat Stahl 2K]

We had a similar problem in my discussion about nicotine, and my TA told us to find the moles of N. That way you can find the empirical formula more easily I think.

[VSU_3F]

Because nitrogen is part of the compound, it is treated as N. Only when the problem states that something is reacted with nitrogen do we treat it as N2 because on its own nitrogen exists as N2.

[Carly_Lipschitz_3H]

I think it's easiest to treat it as N. It's a little easier to find the empirical formula when you do it this way. I've always done it this way and never had any problems. Hope this helps!

[Karina Grover 1A]

I personally believe that it is easier to treat nitrogen as N when trying to find the empirical formula. It can get a little confusing otherwise.

[Arnav Saud 2C]

It's best to treat it as N because it can prevent any confusion that can happen when doing the problem later.

[Mina Tadros 3L]

Since it gives you nitrogen by itself, it would be N2, but you would have to convert moles of N2 to N when dealing with empirical formulas.

[Samudrala_Vaishnavi 3A]

For this question think about it in the context of the problem and that helped me a lot because I was struggling with the same thing. When you find the moles of each element you need to convert them in terms of one mole for the sake of the empirical formula you will write but the nitrogen produced from the combustion reaction is a gas so (N2). So you will have to convert the moles of n2 you have to n by multiplying by 2 but you would use the diatomic molar mass before the conversion just to find the number of moles of n2. You will also use the n number of moles to determine the mass of the oxygen in the empirical formula, which is also in terms on one mole, by multiplying by the molar mass of one atom of n and using it with C and H to find the mass of O.

[Gabriel Nitro 1E]

Hi,

Whenever you are doing empirical formula problems and simplifying the ratios of the moles of its components, always be sure (for the sake of ease) to use moles of just the atom, not it's elemental state.

For instance, use moles of N instead of moles of N2 or use moles of O instead of moles of O2.

Hope this helps! :)

[Heidi Buri 2I]

Hi! To find the moles of Nigrogen, I would treat it as N. I believe you would have to use the amount of N2 to find N. This can be converted using stoichiometry. Once using stoichiometry to find the value of N, you would be able to use this value in the molecular formula.

[Emily Wu 2G]

This is a very good question. If I were you, I would just try to do the problem using Nitrogen as N, however, if the answer is strange, I would then do it as N2 and then covert it back to N for the final equation.

[amara ajon 1d]

Hi,
I'm going to assume you were talking about question M19, for which I personally used N2 in both finding the molecular formula and the later balanced equation for the reaction. It would be possible to do it using either N or N2, but I personally found it easier to consistently treat nitrogen as diatomic when finding the formula and balancing the equation afterward.

[Rainy Liu Ruoshui_2K]

You should find the moles for N, because we want to know the ratio of different atoms in the molecule, caffeine.