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    I really need your opinion in this one:

    Name:  thermoq.PNG
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    I think it is meant to be delta G at standard conditions (not sure). So I calculated delta G and it's negative so option A? I think it's either A or B

    Many thanks. Help will be appreciated
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    (Original post by Daniel Atieh)
    I really need your opinion in this one:

    Name:  thermoq.PNG
Views: 113
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    I think it is meant to be delta G at standard conditions (not sure). So I calculated delta G and it's negative so option A? I think it's either A or B

    Many thanks. Help will be appreciated
    Without an equation it certainly cannot be determined ...

    Option D
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    (Original post by charco)
    Without an equation it certainly cannot be determined ...

    Option D
    The equation is
    deltaG= delta Gْ + RTln ([products]/[reactants])
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    (Original post by Daniel Atieh)
    The equation is
    deltaG= delta Gْ + RTln ([products]/[reactants])
    I meant the equation for the reaction ...
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    (Original post by charco)
    I meant the equation for the reaction ...
    hmm I really don't know. But the reaction is feasible, and we have the concentrations. Lets suppose i have the equation, how i should go about solving it?
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    (Original post by Daniel Atieh)
    hmm I really don't know. But the reaction is feasible, and we have the concentrations. Lets suppose i have the equation, how i should go about solving it?
    Which reaction? There is none stated!
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    (Original post by charco)
    Which reaction? There is none stated!
    I would assume this (didn't check the image, sorry):

    A + B <--> C + D
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    (Original post by Daniel Atieh)
    I would assume this (didn't check the image, sorry):

    A + B <--> C + D
    If it is that equation, and its an equilibrium, then at equilibrium ∆G = 0 so ∆G° = -RT lnK and you can work out the equilibrium ratios. Then just decide whether [A] and [B] will increase or decrease to get to that ratio. (That is assuming the ∆G you've been given is in fact ∆G°. If its ∆G instead, you don't have enough information. I don't really trust the notation of whoever gave you the question though!)
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    (Original post by KombatWombat)
    If it is that equation, and its an equilibrium, then at equilibrium ∆G = 0 so ∆G° = -RT lnK and you can work out the equilibrium ratios. Then just decide whether [A] and [B] will increase or decrease to get to that ratio. (That is assuming the ∆G you've been given is in fact ∆G°. If its ∆G instead, you don't have enough information. I don't really trust the notation of whoever gave you the question though!)
    Hey

    Yes, I confirmed it is delta G at standard conditions. I am given the concentration of each species in the question (1M A, 1M B, 0.1 M C, 0.1 M D).
    So shall I calculate delta G? If so, I got a large negative value, and accordingly, can I say it goes in forward direction? Is this approach correct?

    I still feel pretty weak at grasping what's going on in this question :/
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    (Original post by Daniel Atieh)
    Hey

    Yes, I confirmed it is delta G at standard conditions. I am given the concentration of each species in the question (1M A, 1M B, 0.1 M C, 0.1 M D).
    So shall I calculate delta G? If so, I got a large negative value, and accordingly, can I say it goes in forward direction? Is this approach correct?

    I still feel pretty weak at grasping what's going on in this question :/
    My take on this is that the easiest way to tackle it is to use:

    ΔG = -RTlnK

    To work out K

    Then plug in the values given to find out the reaction quotient K'

    If K' is larger than K the reaction goes in reverse and vice versa.
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    (Original post by charco)
    My take on this is that the easiest way to tackle it is to use:

    ΔG = -RTlnK

    To work out K

    Then plug in the values given to find out the reaction quotient K'

    If K' is larger than K the reaction goes in reverse and vice versa.
    (Original post by KombatWombat)
    If it is that equation, and its an equilibrium, then at equilibrium ∆G = 0 so ∆G° = -RT lnK and you can work out the equilibrium ratios. Then just decide whether [A] and [B] will increase or decrease to get to that ratio. (That is assuming the ∆G you've been given is in fact ∆G°. If its ∆G instead, you don't have enough information. I don't really trust the notation of whoever gave you the question though!)
    Many thanks both of you. I utterly got what you mean, and it worked well.

    My last question is whether I can simple find delta G and according to that I can decide which side it will favour. In our example, it is negative so forward. What do you think?
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    (Original post by Daniel Atieh)
    Many thanks both of you. I utterly got what you mean, and it worked well.

    My last question is whether I can simple find delta G and according to that I can decide which side it will favour. In our example, it is negative so forward. What do you think?
    But you are given ΔG in the question!
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    (Original post by charco)
    But you are given ΔG in the question!
    Delta G at standard conditions.
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    (Original post by Daniel Atieh)
    Delta G at standard conditions.
    The value of ΔG changes during the reaction.

    Do you mean to find ΔG at the beginning of the reaction with only A and B present in stoichiometric amounts? (Don't forget that temperature does not feature in standard conditions)

    I don't see how this is relevant for your question.
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    (Original post by charco)
    The value of ΔG changes during the reaction.

    Do you mean to find ΔG at the beginning of the reaction with only A and B present in stoichiometric amounts? (Don't forget that temperature does not feature in standard conditions)

    I don't see how this is relevant for your question.
    Yes, at that point where we have 1 molar of reactants and 0.1 molar of products. I can calculate delta G for that point and see whether it will occur or not. As I got a negative value, it is feasible and will go towards products. Correct?

    I got your point that delta G changes in the course of the reaction, yeah.
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    (Original post by Daniel Atieh)
    Yes, at that point where we have 1 molar of reactants and 0.1 molar of products. I can calculate delta G for that point and see whether it will occur or not. As I got a negative value, it is feasible and will go towards products. Correct?

    I got your point that delta G changes in the course of the reaction, yeah.
    According to your question the reaction will not start under standard conditions from the reactants A & B

    ΔG is positive.

    But you know that at equilibrium ΔG = 0

    Use the standard ΔG value to work out the equilibrium constant

    And do your calculations using the molar amounts given to find the quotient = [C][D]/[A][ B]
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    (Original post by charco)
    According to your question the reaction will not start under standard conditions from the reactants A & B

    ΔG is positive.

    But you know that at equilibrium ΔG = 0

    Use the standard ΔG value to work out the equilibrium constant

    And do your calculations using the molar amounts given to find the quotient = [C][D]/[A][ B]
    Thank you. Yes, I got this approach and it worked, but I am still keen to know whether the other pathway makes sense or not.

    deltaG= delta Gْ + RTln ([products]/[reactants])
    delta G = (0.4 Kj x 10^3) + [8.314 J/K/mol x 298 K x ln (0.1 x 0.1)/1)] = -11000 J

    Sorry for disturbance, but it is important for me to know why the above method does/doesn't work
 
 
 
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