i need help in chemistry "Thermodynamics and the equilibrium constant"

[vincikai]

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Thermodynamics and the equilibrium constant

Okay I have a question about the equation (* means change) (*() means stander condition) so [G=*(G)+RT ln (Keq)] or just equation *(G)= - RT ln(Keq)
So what dose the (Keq) stander for??? Kc? Kp? Ksp?? Kf or Kd

Is it always Kc regardless the chemical reaction? (that's what my prof told me)
And then use the equation Kp=Kc (RT)^*n to convert K value???

Or is does Keq depends on the chemical reaction Kc for solution Kp for Gas???(from the text book)

And can someone please derived the equation [G=*(G)+RT ln (Keq)] for me?
Where is it come from and why does it makes sense?

 

[shantster]

Thermodynamics and the equilibrium constant

Okay I have a question about the equation (* means change) (*() means stander condition) so [G=*(G)+RT ln (Keq)] or just equation *(G)= - RT ln(Keq)
So what dose the (Keq) stander for??? Kc? Kp? Ksp?? Kf or Kd

Is it always Kc regardless the chemical reaction? (that’s what my prof told me)
And then use the equation Kp=Kc (RT)^*n to convert K value???

Or is does Keq depends on the chemical reaction Kc for solution Kp for Gas???(from the text book)

And can someone please derived the equation [G=*(G)+RT ln (Keq)] for me?
Where is it come from and why does it makes sense?

I've never seen all those different Ks before, but I'll explain what I know.

Keq is the equilibrium constant. It's the equilibrium value of [Products]/[Reactants]

Ksp is the solubility constant. Same thing as Keq since it's the constant for at equilibrium, but you have to remember that the pure solids aren't factored into it so it really becomes Ksp = [Products] = [Ion1][Ion2] if two ions, add ion3 and ion4, etc. if have more ions.

Q is the value for the prevailing conditions, not equilibrium. It is calculated by the same was as the previous K's described, but the prevailing conditions (not equilibrium conditions) are used. You can also compare Q and Keq to determine which way the reaction will go:

If Q>K, then have more products than want at equilibrium and so reaction goes toward reactions.
If Q<K, then have more reactants than want at equilibrium and so reaction goes toward products.
If Q=K, then at equilibrium.

Deriving equations is tricky to do online (due to formatting), so I'd ask your prof to do it since it would take less time for him/her to explain it and would make a whole lot more sense than if I tried to show you it online.

Hope this helps!

 

[Sinbadthesailor]

i thought Kp=partial pressures of products divided by partial pressures of reactants. i.e. A+B=2C means Kp=Pc^2/(Pa*Pb)
Kc would be for concentrations. Concentration is Partial Fraction of the components. In this example: Kp=Pt^2*[C]^2/(Pt*[A]*Pt*), where Pt is total pressure. Here Pt cancells out, so Kp=Kc=[C]^2/([A]*)

but if you have an equation like A+B=C, then Kp=Pt*[C]/(Pt*[A]*Pt*)=Kc/Pt so they're not always equal.

deltaG=deltaG0+RTlnKp. At equalibrium deltaG=0, so deltaG0=-RTlnKp.
if you wanted to derive why Kp and not Kc, it's because for an individual component Gi=G0+RT*ln(Pi/1atm). and deltaG is the sum of Gi's of products minus reactants. i dont know about Ksp--we didnt cover that in chem class.