# Chemistry

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Each molecule of NO2, nitrogen dioxide, consists of 1 atom of N and 2 atoms of O. If you have 0.155 g. of NO2, how many molecules of NO2 do you have ?
If you could, please include steps as to how to do the problem.
Thank you

• Chemistry - ,

How many moles NO2 do you have? That is grams/molar mass = 0.155/46.0 = about 0.003 (but you need to do it more accurately).
1 mole NO2 contains how many molecules NO2. 1 mole of NO2 contains 6.022E23 molecules; so how many molecules NO2 do you have? That is 0.003 moles NO2 x (6.022EE23 molecules/mole) = about 2E21.

• Chemistry - ,

Thank you :)
Part 2:
How many atoms of N do you have ?

• Chemistry - ,

Many profs will count your answer as incorrect. By placing that many zeros after the number you indicate there are 21 significant figures and that isn't correct. There are only 3 (dictated by the 0.155 gram in the initial sample) so the correct way to show this is 2.03E21.
For the correct number of N atoms, there is 1 N per NO2 molecule; therefore, the number of atoms N is the same as the number of molecules of NO2. There will be twice that number for the number of O atoms.

• Chemistry - ,

Our work is online, and I tried to enter it as 2.03E21 and it would not accept it.
It only accepts the answer if everything is correct.
Thank you :)

• Chemistry - ,

OK. I suppose you play the game the way it works; however, 2.03E21 is the correct way of writing that number.

• Chemistry - ,

Than you can be the one to tell my prof that, sir :)