[xitenshiix]

I have a problem that I need help again with.

So for this review worksheet it says:

Calculate the percent composition of the compound that is formed when 9.03g magnesum combines completely with 3.48 g nitrogen.


Okay so we're learning about moles and avagadro's number, also i know how to find the percent of an element but my teacher ran out of time before explaining this to our class. She also told us that we were responsible for this knowledge. However how to figure out this problem I have no idea as to how I might go about answering this question so if anyone could help me and explain how you answer this kind of problem that would be a big help. And please dont just give me the answer because I am responsible for this information.

Thank you

[lemonoman]

Try http://www.chemicalforums.com/index.php?board=4;action=display;threadid=3023

If you need anything else, just let us know

[xitenshiix]

yea ^^ i knew that, though my question is how do you find the percentage of the compound formed when 9.04 oxygen ect... the question i had up there. The link you provided me with is about percent composition but isn't relavent to my question. But thanks!

[kkrizka]

Do you want percentage composition by mass or number of atoms?

For mass, just find the total mass (add them together) and divide the amount of each element by this amount.

or by the amount of elements. You need to convert the mass to the amount of atoms it is. To do this, you divide by something called "molar mass". It basically is how much a mole of an atom/molecule weights and is the same as the atomic mass, exept in grams. Now that you know how many moles you have, do the same as with mass. A way to check this is by seeing what molecule it gives you. So if we look at the periodic table, you should see that Mg and N combines to form Ng3N2. So this is 60% (3/5) Mg and 40% (2/5) Nitrogen. Which are the same numbers I got when I tried to solve your question.

If you need more help, I suggest consulting google.