Homework Help: Chemistry

Posted by Mike on Wednesday, January 9, 2008 at 8:37pm.

Can someone check my answers for me thank you. This is my 3rd time posting this one up...maybe its just not going through bc I don't see it on the current ?s.

4NH3 + 7O2 --> 4NO2 + 6H2O

1)How many grams of oxygen are necessary to produce 4.50 moles of NO2?

answer: 252 grams

2)How many molecules of water are produced when 2.25 moles of ammonia are completely reacted?

answer: 3.38 moles

Chemistry - DrBob222, Wednesday, January 9, 2008 at 8:50pm
I haven't seen any of this question before and I've checked from time to time today. At any rate, your answer to #1 is correct. Your answer to #2 is not. You have correctly given the answer in moles (to #2) BUT the question is how many molecules (and not moles). Remember 1 mol H2O will have 6.02 x 10^23 molecules; therefore, 3.376 mol H2O will have ?? molecules.
- Chemistry - DrBob222, Wednesday, January 9, 2008 at 8:52pm
  I made a typo. That's 3.375 mols and not 3.376. I usualy carry the extra places, then round at the end to prevent rounding errors.
Chemistry - Mike, Wednesday, January 9, 2008 at 10:48pm
So the answer to #2 would be...2.03x10^24 molecules?
- Chemistry - DrBob222, Wednesday, January 9, 2008 at 11:48pm
  yes

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