## Different ways of approaching 10.23

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Kayla Denton 1A
Posts: 106
Joined: Fri Sep 26, 2014 2:02 pm

### Different ways of approaching 10.23

Hi! The way I approached question 10.23 in the textbook (written below) is different than the approach in the solutions manual. I was wondering if my way was valid as well?
Thanks!
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Niharika Reddy 1D
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### Re: Different ways of approaching 10.23

I think the way you approached it is valid as well, but since they gave the reaction quotient Q in the problem, they probably wanted us to find K to compare the two values and determine the direction the reaction will have a tendency to go in from there.

As you said, both methods yield the same answer, but since Q was given, I feel like it must've been given for the purpose of comparing it with K after calculating K.

Chem_Mod
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### Re: Different ways of approaching 10.23

Niharika is correct, the two methods are actually exactly the same.

$\Delta G^{\circ} = -RTlnK$
$\Delta G = \Delta G^{\circ} + RTlnQ = -RTlnK + RTlnQ = RTln(Q/K)$

So if Q/K < 1, log will be negative and process is spontaneous
If Q/K > 1, log is positive and process is not spontaneous