Gibbs Free Energy - GRE Subject Test: Chemistry
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At 
, a reaction has a Gibb's free energy change of 
. If the enthalpy change of the reaction is 
, what is the entropy change of the reaction?
At
We can relate enthalpy, entropy, and Gibb's free energy using the Gibb's free energy equation:
Keep in mind that temperature must be in Kelvin. Since we know enthalpy and Gibb's free energy for the reaction, we can solve for the entropy change:
We can relate enthalpy, entropy, and Gibb's free energy using the Gibb's free energy equation:
Keep in mind that temperature must be in Kelvin. Since we know enthalpy and Gibb's free energy for the reaction, we can solve for the entropy change:
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Which of the following options indicates that a chemical reaction is unfavorable?
Which of the following options indicates that a chemical reaction is unfavorable?
The sign of 
indicates the direction of a chemical reaction and determines if a reaction is spontaneous or not. A chemical reaction in which 
is considered to be a spontaneous reaction because it will proceed without requiring any outside energy. To approach this problem, we must consider the equation for the Gibbs free energy of a reaction, 
. A reaction is considered to be favorable when is negative. The second law of thermodynamics indicates that the entropy of the universe is spontaneously increasing. This corresponds to a positive 
.
The sign of
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