The concentration of B at equilibrium

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Discussion Overview

The discussion revolves around determining the concentration of B at equilibrium for the reaction A(g) + 2B(g) --> C(g), given initial amounts of A and B in a container and the equilibrium concentration of A. The scope includes homework-related problem-solving and mathematical reasoning.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant identifies B as the limiting reactant (LR) based on the initial moles of A and B and questions whether the reaction goes to completion.
  • Another participant suggests that the concentration of C is not needed to solve the problem.
  • A participant expresses uncertainty about determining when the reaction stops and notes that A and B decrease to produce C.
  • There is a suggestion to think in terms of stoichiometry to relate the concentrations of A, B, and C.
  • One participant proposes a calculation for the concentration of B based on the concentration of A, but this is challenged by another participant who emphasizes the need to calculate moles and reactions explicitly.
  • A later reply introduces the concept of an ICE table as a potential tool for organizing the information needed to find the concentration of B.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to approach the problem or the necessary information to solve it. There are multiple competing views on the relevance of certain data and methods.

Contextual Notes

Participants express uncertainty regarding the completion of the reaction and the need for additional information, such as the equilibrium constant or the concentration of C. The discussion reflects a lack of clarity on how to effectively apply stoichiometric principles in this context.

Who May Find This Useful

Students working on equilibrium problems in chemistry, particularly those involving stoichiometry and limiting reactants.

JessicaHelena
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Homework Statement


For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00L container.
A(g) + 2B(g) --> C(g)
At equilibrium, the concentration of A is 0.246 mol/L. What is the concentration of B at equilibrium?

Homework Equations


for aA+bB-->cC,
K = [C]^c/([A]^a[ B]^b)

c=n/V

The Attempt at a Solution


Frankly, I'm not sure what to do here. The LR is B since using all 3.00 moles of B, we'd only need 1.5 moles of A, but that's when the reaction goes to completion and we don't know if it does. Also, we are not given C's concentration or the K value... What can I do here?
 
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JessicaHelena said:
The LR is B since using all 3.00 moles of B, we'd only need 1.5 moles of A, but that's when the reaction goes to completion and we don't know if it does.
That's something you can figure out

JessicaHelena said:
Also, we are not given C's concentration or the K value...
It is not given because it is not needed.

JessicaHelena said:
What can I do here?
What happens to A and B when you mix them? What is the relation between the concentrations of A, B and C?
 
how can I figure at which point the experiment stops — I'm still not so sure.

The amount of A and B decrease to produce C.

concentrations of A:B:C = # of moles of A:B:C
 
Think in terms of a simple stoichiometry.
 
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So then at equilibrium, there'd be 0.246 mol/L of A, and 0.246 x 2 mol/L of B and 0.246 mol/L of C?
 
No. you have the concentration of A, and the volume. How many moles of A are there?
So how many moles of A have reacted?
How many moles of B have reacted, and how many are left?
What is the concentration of B?
Have you heard of an ICE table?
 

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