Julie S. answered • 07/26/16
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Chemistry Can Be Fun! 25 Years Tutoring Gen Chem and Orgo Chem
The relevant equation is ΔG° = -RTlnK This equation relates the standard Gibbs Free Energy change to the equilibrium constant. Remember, if ΔG° is negative, that means the reaction is spontaneous as written, and therefore the products are thermodynamically favored at equilibrium. This means that K will be "large" (greater than 1). The reverse is also true - positive ΔG° means K will be "small" and reactants favored at equilibrium.
In the equation, R is the gas constant in thermodynamic terms, 8.314 J/mol•K. T is the absolute temperature in K, and you have that value as 298K. The rest is plugging in and solving:
ΔG° = - (8.314 J/mol•K)(298K)(ln 1.8 x 10^-7)
ΔG° = - (8.314 J/mol•K)(298K)(-15.53)
ΔG° = +38477 J/mol = +38.477 kJ/mol = +38 kJ/mol (two sig figs in answer because only 2 sig figs in the K value)
Notice this result forΔG° is (+) and K was very small! ;)
