Solving Gas Laws: 3H2 + N2 -> 2NH3 at 110 ATM

  • Thread starter Thread starter Lancelot59
  • Start date Start date
  • Tags Tags
    Gas Gas laws Laws
Click For Summary

Discussion Overview

The discussion revolves around a gas law problem involving the reaction of hydrogen and nitrogen to form ammonia under specific conditions. Participants are attempting to calculate the equilibrium constant (Kp) for the reaction given the total pressure and volume percentages of the gases involved, while addressing issues related to the ideal gas law and the determination of partial pressures.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents an ICE table approach to calculate the volumes of gases involved in the reaction but expresses uncertainty about the correctness of their method.
  • Another participant suggests that the initial approach may be on the right track but does not provide specific corrections.
  • A participant raises concerns about not knowing the number of moles of each gas, which complicates the determination of concentrations and pressures.
  • One participant inquires about calculating the partial pressure of ammonia at equilibrium and how to relate it to the total pressure of the gas mixture.
  • Another participant argues that while the ideal gas law may not be directly applicable, the number of moles can be inferred from the volume ratios of the gases.
  • A participant expresses confusion regarding the application of mole fractions and how they relate to the empirical formula of the gas mixture.
  • One participant clarifies that mole fractions can be used to calculate pressures using Dalton's law, suggesting a more systematic approach to the problem.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct method to solve the problem, and multiple competing views on how to approach the calculations remain evident throughout the discussion.

Contextual Notes

Participants express uncertainty regarding the assumptions made in their calculations, particularly concerning the initial volumes and the relationship between volume and moles of gas. There is also a lack of clarity on how to effectively apply Dalton's law in this context.

Lancelot59
Messages
640
Reaction score
1
It's a gas problem:

3 volumes N2 and 1 volume of H2 react at 344 degrees Celsius to form NH3. The equilibrium total pressure is 110 ATM and is 41.49% NH3 by volume. Find Kp assuming the gases behave ideally.

So I started by assuming that I had 100L of gas. I worked the ICE table like so:

3H2 + N2 <--> 2NH3
75L_____25L_____0L
-3x_____-x______+2x
12.765L_4.255L___41.49L

Well this gives me volumes. But it's wrong. This is clearly not working. How can I go about it correctly?
 
Physics news on Phys.org
Why is it not working? I can be missing something, but I think you are on the right track, just not there yet.
 
Last edited by a moderator:
Well to be honest I have no idea what to do now. I have their volumes, but without knowing how many mols of each I have I can't determine their concentrations. Also, I started with 100L, and ended up with only 58.51L at equlibrium...something seems wrong there.
 
Can you calculate partial pressure of the ammonia at equilibrium? Sum of partial pressures of other gases? Assuming you started with stoichiometric mixture of gases, can you split this sum into pressures of other gases?
 
I can't see a way to get the pressure of ammonia. I don't know how many mols I have, so the ideal gas law is out.
 
Not exactly out.

Number of moles of gas is - for a given p, T - directly proportional to its V. If gas occupies half the volume, it also has half the moles of the mixture. This will not give you number of moles, but it will give you their ratio.
 
Last edited by a moderator:
I see where you're going, but I'm confused.

Lets say this fake gas at 110atm is: 30% X 60%Y and 10%Z by pressure. The empirical formula for the mixture is 3X 6Y Z?
 
You can put it that way, although it is better to say that mole fraction of X is 0.3, of Y 0.6 and of Z 0.1. Then you can use molar fractions to calculate pressure (Dalton's law).
 

Similar threads

2NH3->N2+3H2. Rate=k[NH3]/[H2], what is the mechanism?
  • · Replies 1 ·
Replies
1
Views
13K
Chemistry Calculation of thermodynamic variables for irreversible adiabatic process of ideal gas
  • · Replies 9 ·
Replies
9
Views
3K
Reaction of gases/ gas stoichiometry
  • · Replies 3 ·
Replies
3
Views
5K
Ideal Gas Law solve for partial pressure
  • · Replies 2 ·
Replies
2
Views
4K
Will reversing Avogadro's Law lead to equal volumes for equal moles of gas?
  • · Replies 8 ·
Replies
8
Views
6K
Uncovering the Chemistry Behind Ammonia Production
  • · Replies 6 ·
Replies
6
Views
3K
Trouble solving for end state of two control volumes in a rigid tank
  • · Replies 12 ·
Replies
12
Views
3K
Solving the ideal gas law for volume -&gt; length
  • · Replies 1 ·
Replies
1
Views
17K
Ideal Gas Law: messing with ratios
  • · Replies 7 ·
Replies
7
Views
3K
Ideal Gas Law in "alternate" universe
  • · Replies 4 ·
Replies
4
Views
3K