Kaplan Thermochem Problem

[Hexon]

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from the kaplan gen chem book, p124, the question:

If a pyrophosphoric acid and arsenous acid have acid dissociation constants of 3x 10^-2 and 6.6 x 10^-10, respectively, at room temp. find the gibbs free energy of each dissociation reaction and determine if it's spontaneous. what does this mean for delta H and delta S for these reactions?

i understand the second part of the question but am stuck on how to use the acid dissociation constants to find the values i need🙁

 

[Pisiform]

Delta G = -RT ln Keq ...... Keq is same as Ka.

 

[Hexon]

Delta G = -RT ln Keq ...... Keq is same as Ka.

nice, and thanks Pisiform.

btw do we have to know the Gas Constant for the MCAT?
seems kinda excessive😛

 

[Pisiform]

nice, and thanks Pisiform.

btw do we have to know the Gas Constant for the MCAT?
seems kinda excessive😛

Yep it's easy but most probably they will give you in a passage.

 

[MT Headed]

The real mcat is always seems to have lots of constants at thd end of passages. Although they might not tell you how to use them, the units alone are a big help. My favorite was once they told me faraday's constant, in units of "23 kcal per mol-volt". This saved me a lot of conversions, but it is one hell of a convoluted way to tell somebody that a coulomb (6 10^18) is smaller than a mole (6 10^23) by 5 orders of magnitude.

 

[Erythropoietin]

nice, and thanks Pisiform.

btw do we have to know the Gas Constant for the MCAT?
seems kinda excessive😛

I would know the two numbers of R 8.31 and the other one was 0.082 I believe

 

[Hexon]

i appreciate the help, ladies and gents🙂

may the flying spaghetti monster bless you all with manly children😛