Calculating Fraction of A Dissociated at 1000K with 1 atm and 10^-3 atm Pressure

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Discussion Overview

The discussion revolves around calculating the fraction of a gas A that dissociates into gas B at a temperature of 1000K under two different total pressures (1 atm and 10^-3 atm). Participants explore the relationship between partial pressures and the equilibrium constant for the reaction A(g) -> 2B(g).

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents the equilibrium constant and attempts to calculate the dissociation fraction using the ideal gas law and the relationship between partial pressures.
  • Another participant suggests solving the problem in terms of partial pressures and questions the sum of the partial pressures.
  • There is a discussion about the correct formulation of the relationship between partial pressures, with some confusion about the definition of partial pressure and the correct equations to use.
  • A participant proposes using simultaneous equations to relate the partial pressures of A and B, leading to a quadratic equation.
  • One participant arrives at a solution for pB and subsequently calculates pA based on that result.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the correct formulation of the equations and the definitions involved. There is no consensus on the best approach to solve the problem, and multiple viewpoints on the relationships between the variables are presented.

Contextual Notes

Participants demonstrate varying levels of understanding regarding the application of the equilibrium constant and the use of partial pressures. Some assumptions about the definitions and relationships may not be fully clarified.

Who May Find This Useful

This discussion may be useful for students studying chemical equilibrium, particularly those working on problems involving gas dissociation and partial pressures in thermodynamics.

cantgetno
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Homework Statement


The Equilibrium constant for A(g) -> 2B(g)
is 1x10^-2 at 1000k. Calculate the fraction on A which is dissociated at 1000k if the total pressure is
1 atm
10^-3 atm

Homework Equations


PV=nRT
B^2 / A = Ke (1x10^-2)

The Attempt at a Solution


for A PV=1x8.714x1000 = 8.714x10^3
for B PV=2x8.714x1000 = 17.428



All i can work out from this is that there's gunna be a 1:2 ratio? I am completely lost and my minds gone blank. Thanks in advance for the help
 
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Solve in terms of partial pressures. What is sum of pA and pB?
 
surely it would be pA+2pB=1atm ?
and I am not very sure how to solve in terms of partial pressures

would i have
kp= pB^2 / pA
so 0.01 = pB^2 / pA

I've tried using a simultaneous equation with pA+2pB=1
and just end up with rubbish
 
Why pA + 2 pB? Do you know definition of partial pressure?
 
because there's 2 moles of it? i thought that was right, my bad.

pA+pB=1atm that right?
would i be right to use a simlt equ then?
 
2*yes.
 
ok using the equations i end up with the quadratic:
pB^2 + 0.01pB-0.01=0 so pB=0.095atm
so pA=0.905atm
and i can work out for the other atmthanks
 

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