Partial Pressures: Solving Complex Equations

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Discussion Overview

The discussion revolves around the calculation of partial pressures and the conservation of mass in a closed system, specifically in the context of a homework problem involving the moles of nitrogen dioxide (NO2) and dinitrogen tetraoxide (N2O4). Participants explore the relationships between the moles of these gases and the total moles of gas present.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions the reasoning behind the equivalency of moles of NO2 and N2O4 in relation to total moles, suggesting it might be the other way around.
  • Another participant proposes that 0.330 moles refers to the total moles of gas in the flask, expressing uncertainty about the validity of the equivalency presented.
  • There is a discussion about the conservation of nitrogen atoms throughout the reaction, with one participant asserting that the number of nitrogen atoms remains constant.
  • Participants clarify the moles of nitrogen atoms per mole of NO2 and N2O4, with some stating that there is one mole of nitrogen in NO2 and two moles in N2O4.
  • Further clarification is sought on how many moles of nitrogen atoms are present in a mixture of NO2 and N2O4, leading to a calculation involving n moles of each gas.
  • One participant emphasizes that the initial amount of nitrogen atoms does not change, prompting a return to the original text for further analysis.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the calculations and relationships between moles of gases and nitrogen atoms. There is no consensus on the initial question about the equivalency of moles, and several points remain contested or unclear.

Contextual Notes

Some participants reference the definitions of moles and the conservation of mass, but there are unresolved assumptions about the initial conditions and the specific calculations involved in the problem.

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Homework Statement



http://i.minus.com/jbzyIAyMvUrADW.png

Homework Equations



Conservation of mass in a closed system.

The Attempt at a Solution



I'm not sure what the lecture is getting at here. Why is it that the number of moles of NO2 added to twice the number of moles of N2O4 = the total moles? Shouldn't it be the other way around?
 

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Number of moles of what is calculated?
 
I think 0.330 moles refer to the total moles of gas in the flask. I'm not sure why the equivalency on the bottom of the slide holds.
 
Qube said:
I think 0.330 moles refer to the total moles of gas in the flask.

Have you READ the text you posted? It clearly explains what is calculated.
 
I don't understand what I posted
 
Do you understand

0.330 mol of NO2 and therefore the same number of moles of nitrogen atom atoms

?
 
I understand that but nothing else.
 
Does the number of moles of N atoms change throughout the reaction?
 
No, there are two moles on either side
 
  • #10
OK (although the reason is slightly different - mass is conserved, nitrogen is not produced out of nothing, actually the fact that there are two moles on both sides on of the reaction equation is a conclusion of the mass conservation, not a proof of the mass conservation as you seem to be implying. Also, it doesn't have to be two moles - what if you start with half o mole of nitrogen atoms?).

There is an identical amount of nitrogen atoms before and after the reaction.

How many moles of nitrogen atoms per mole of NO2?

How many moles of nitrogen atoms per mole of N2O4?
 
  • #11
There are n moles of nitrogen atoms per mole of NO2 and 2n moles of nitrogen atoms per mole of N2O4.
 
  • #12
No, not "n moles" per mole. n has a well known value.

What is a mole definition?
 
  • #13
There is one mole of N in one mole of nitrogen dioxide. And two moles of N in one mole of dinitrogen tetraoxide
 
  • #14
OK, you have a mixture of nNO2 (containing 1 mole of nitrogen atoms per one mole of gas) and nN2O4 (containing 2 moles of nitrogen atoms per one mole of gas). How many moles of nitrogen atoms are in the mixture?
 
  • #15
There are n plus 2n moles of nitrogen.
 
  • #16
More specifically, the first n refers to nitrogen dioxide and the second n refers to dinitrogen tetraoxide.
 
  • #17
OK, so now you know that the mixture contains nNO2+2nN2O4 moles of nitrogen atoms, you know that initially there were 0.330 moles of nitrogen atoms, and you know that amount of nitrogen atoms didn't change. Get back to the original text.
 

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