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# finding eq'm constant watch

1. I did a prac for change in gibbs free energy but I need K of reaction

HCl + NaOH --> NaCl + H2O (1)
i think i'm meant to be looking at H+ + OH- <-> H2O (2)

i put 50cm3 of each 0.5M conc together in a calorimeter and measured temp change and found change in heat enthalpy
now want change in gibbs = RTln(K)

they say i should know K already, idk if they meant just Kw but with acid and base i dont know and cant find anywhere how to get K. I know K = product of conc to power of coeaffs of products / same with reactants, they say to look at eq'n (2) in reverse to help?
2. (Original post by Nat_LPS)
I did a prac for change in gibbs free energy but I need K of reaction

HCl + NaOH --> NaCl + H2O (1)
i think i'm meant to be looking at H+ + OH- <-> H2O (2)

i put 50cm3 of each 0.5M conc together in a calorimeter and measured temp change and found change in heat enthalpy
now want change in gibbs = RTln(K)

they say i should know K already, idk if they meant just Kw but with acid and base i dont know and cant find anywhere how to get K. I know K = product of conc to power of coeaffs of products / same with reactants, they say to look at eq'n (2) in reverse to help?
You do know that Kw = 1 x 10-14

And that it applies to the equilibrium:

H2O <==> H+ + OH-

This is the reverse of the equation of the reaction that you are studying thermodynamically.

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