[superjames1992]

Hello, this is my first post here, so greetings!

I am currently in Chemistry 101 and I was doing some HW online on Webassign earlier when I can across a problem which perplexed me because I think that it is incorrect.

The question was:

How many moles of molecules and atoms are in a 6.7 g sample of CH₄? Use the following atomic masses: C=12, H=1

So, I took the mass of CH₄, which is 16 g and divided 6.7g/16g, which gave me 0.41875 moles of molecules.  This was correct as Webassign put a green check mark by it.

But then I went on to do the second part and multiplied 0.41875 x (6.022 x 10²³), which gave me 2.5217125 x 10₂₃.  I put this in Webassign as 2.522e23.  However, it gave me a red x twice and I am not sure what I am doing wrong or whether the system's answer key is wrong.  I asked my roommate and he had the same problem.

Do you all know what I did wrong?

[FreeTheBee]

The question is how many moles of molecules and how many moles of atoms there are in the sample. You know how many moles of CH4 you have, but how many atoms are there in one CH4 molecule?

[superjames1992]

The question is how many moles of molecules and how many moles of atoms there are in the sample. You know how many moles of CH4 you have, but how many atoms are there in one CH4 molecule?

Thank you for the assistance!  I finally figured it out.  I'm not sure why I was trying to come up with the number of atoms when it was asking for how many moles of atoms there were.  

I ended up taking 5 x 6.7 and getting 33.5.  Then I took 33.5 and divided into my molecule's mass, 16 g, and got 2.09375 moles of molecules.

[opti384]

I ended up taking 5 x 6.7 and getting 33.5.  Then I took 33.5 and divided into my molecule's mass, 16 g, and got 2.09375 moles of molecules.

I think you still misunderstood something. Your first answer of 0.41875 moles of molecules is correct. I thought you were supposed to find how many moles of C and H atoms in 6.7g of CH₄.