Chem Equil: CH4 + H2S -> CS2 + H2 - Calc \[CS_2\] at Equil

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Discussion Overview

The discussion revolves around calculating the equilibrium concentration of CS2 in the reaction CH4 + 2H2S <=> CS2 + 4H2, given certain amounts of reactants at equilibrium. Participants explore the implications of the problem statement and the necessary calculations involved.

Discussion Character

  • Homework-related
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about the problem statement, questioning the definition of "reactants" and whether it refers to the left-hand side of the equation.
  • Another participant suggests that if "reactants" are interpreted as substrates, the problem becomes easier to solve.
  • There is confusion regarding the number of unknowns in the problem, specifically the amounts of CS2 and H2 at equilibrium.
  • A participant proposes a method to calculate the equilibrium concentration of CS2, using the equilibrium constant and the amounts of CH4 and H2S provided.
  • Participants discuss the initial amounts of substances and how they relate to the equilibrium concentrations.
  • One participant calculates that the amount of CS2 at equilibrium is 0.323 mol, but this is presented as part of their reasoning process rather than a definitive conclusion.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the problem statement and the definitions of reactants versus substrates. There is no consensus on how to approach the problem, and multiple interpretations remain unresolved.

Contextual Notes

Participants note the lack of clarity in the problem statement and the potential for different interpretations regarding the terms used. The discussion highlights the presence of two unknowns, which complicates the calculations.

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Reaction: [itex]CH_4 + 2H_2S <-> CS_2 + 4H_2[/itex]
[itex]k_{eq} = 100[/itex] at a certain temperature

An unkown amount of reactants were intorduced into a 1.0L bulb and at equilibrium 0.10 mol of [itex]CH_4[/itex] and 0.30 of [itex]H_2S[/itex] were found. Calc [itex]\[CS_2\][/itex] at equilibrium.

I don't seem to have enough information here. I can form the equation for [itex]k_{eq}[/itex] but I have two unknowns...
 
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Lousy problem statement: the idiot who wrote it mentally equates "reactants" with materials on "left-hand side of equation." Help?
 
Reactants or substrates? If reactants, there is no way to solve the question. If substrates, it is easy.

Two unknowns - you mean amounts of CS2 and H2?

Oops, Bystander was faster :)
 
cscott I tried to resolve this. But before I show how I think this might be done, I want to make sure that I am right. Is the amount of [itex]\[CS_2\][/itex] at equilibrium 0.323 mol ?
 
Bystander said:
Lousy problem statement: the idiot who wrote it mentally equates "reactants" with materials on "left-hand side of equation." Help?

That idiot would be me :rolleyes:. Sorry.

Reactants or substrates? If reactants, there is no way to solve the question. If substrates, it is easy.

I've never heard of "substrates" before. We just barely learned that the reactions go both ways :-p, so I guess that's why I associated reactants with the LHS.

Two unknowns - you mean amounts of CS2 and H2?

Yes.

But before I show how I think this might be done, I want to make sure that I am right.

I didn't get the answers for this practice sheet yet. Maybe you can show your method anyway?
 
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cscott said:
That idiot would be me :rolleyes:. Sorry. (snip)

Huh? You didn't write the problem, you're trying to solve it. All I was doing was translating what was meant by "reactants" as a hint for you.
 
Bystander said:
Huh? You didn't write the problem, you're trying to solve it. All I was doing was translating what was meant by "reactants" as a hint for you.

The problem originally stated the two molecules on the LHS instead of "reactants". I was just being lazy.

I'm still not sure how to get the concentration of [itex]H_2[/itex] at equilibrium to in turn get it for [itex]CS_2[/itex]
 
I didn't get the answers for this practice sheet yet. Maybe you can show your method anyway?

Ok. Here it goes.

First, let's identify the initial amount of the various substances, reactants and products:
CH4 -> n mol
H2S -> m mol
CS2 -> 0 mol
H2 -> 0 mol

At equilibrium according to the stoichiometric coefficients of the substances their amount should be:
CH4 -> n - x mol
H2S -> m - 2x mol
CS2 -> x mol
H2 -> 4x mol

Nevertheless, the problem gives us the amount at equilibrium of CH4 and H2S which are respectively 0.10 mol and 0.30 mol.

Then, we must apply the chemical equilibrium formula using the equilibrium constant given by the problem:

100 = x(4x)^4) / (0.10 x 0.30^2)

Now, it's math.
x will be equal to 0.323 mol

Hope I could help.
 
Thanks PPonte.
 

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