Equilibrium: Final ClBr Concentration 0.15M/L

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Discussion Overview

The discussion revolves around a chemistry homework problem involving the equilibrium concentration of ClBr in the reaction IBr + Cl2 <-> ClBr + ICl, given a specific equilibrium constant (K=4). Participants explore the calculations and assumptions related to the equilibrium state, focusing on the final concentration of ClBr.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant proposes using an ICE table to calculate the equilibrium concentrations, initially finding a value for x but later correcting it to 0.15.
  • Another participant suggests a different approach, indicating that if x mol of IBr and Cl2 react, the equilibrium concentrations can be expressed in terms of x, leading to a calculation of x=0.33 mol.
  • A question is raised about whether Ksp calculations should use molarity instead of moles, indicating a potential misunderstanding of the application of equilibrium constants.
  • A further clarification is made regarding the dependence of calculations on the state of the reactants and products, emphasizing that for gaseous reactions, the distinction between moles and molarity may not affect the outcome.

Areas of Agreement / Disagreement

Participants express differing views on the correct approach to calculating the equilibrium concentrations and whether to use molarity or moles in their calculations. The discussion remains unresolved with multiple competing views presented.

Contextual Notes

Participants have not reached a consensus on the correct method for calculating the equilibrium concentrations, and there are unresolved assumptions regarding the state of the reactants and products.

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Homework Statement



1 mol of each of the following gases is set up with the reaction K=4

IBr + Cl2 <-> ClBr + ICl

Find the final concentration of ClBr

Homework Equations



k= products/reactants

The Attempt at a Solution



First find Q to be 1 by finding the molarity of each gas to be 1/4 M/L. Q<K Therefore equilibrium must shift to right. Set up ICE table as follows:

4 = (1/4+x)2
--------------------
(1/4-x)2

x= 3.75?

nvm x should be = 0.15. Calculation mistake.
 
Last edited:
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Hi Hockeystar!
Maybe it is easier to thing of the problem the following way: in the beginning you had 1 mol of each gas, then as K=4 some amount of reagents is used up and more of the products are formed.
If x mol IBr and x mol of Cl2 reacted to form more products then at equilibrium the amounts of gases will be these: 1+x mol of ICl and BrCl, and 1-x mol of IBr and Cl2, thus
K=(1+x)^2/(1-x)^2=4, x=0,33 (mol).
 
But I thought when calculating Ksp the products and reactants must be molarity, not moles?
 
Actually it depends on the temperature of the reaction vessel. My assumption was that all the reactants and products are gaseous and thus it wouldn't matter whether you take molarities or quantities, because volumes cross out anyway.
 

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