Classifying Reactions - GRE Subject Test: Chemistry
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The equation for the change in Gibbs free energy is given below.
ΔH = change in enthalpy
ΔS = change in entropy
Which of the following scenarios guarantees a nonspontaneous reaction?
The equation for the change in Gibbs free energy is given below.
ΔH = change in enthalpy
ΔS = change in entropy
Which of the following scenarios guarantees a nonspontaneous reaction?
A positive value for ΔG (Gibbs free energy) will guarantee a nonspontaneous reaction. When ΔH (enthalpy) is postive and ΔS (entropy) is negative, the change in Gibbs free energy must be positive and, therefore, nonspontaneous.
Because T (temperature) will always have a positive value, a negative entropy and positive enthalpy will always result in a positive Gibbs free energy.
A positive value for ΔG (Gibbs free energy) will guarantee a nonspontaneous reaction. When ΔH (enthalpy) is postive and ΔS (entropy) is negative, the change in Gibbs free energy must be positive and, therefore, nonspontaneous.
Because T (temperature) will always have a positive value, a negative entropy and positive enthalpy will always result in a positive Gibbs free energy.
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The equation for the change in Gibbs free energy is given below.
ΔH = change in enthalpy
ΔS = change in entropy
In which of the scenarios will the reaction be spontaneous?
The equation for the change in Gibbs free energy is given below.
ΔH = change in enthalpy
ΔS = change in entropy
In which of the scenarios will the reaction be spontaneous?
All of the following scenarios would lead to spontaneous reaction, since each scenario would result in a negative Gibbs free energy (-ΔG).
Negative enthalpy, positive entropy:
Positive enthalpy and entropy with high temperature:
Negative enthalpy and entropy with low temperature:
All of the following scenarios would lead to spontaneous reaction, since each scenario would result in a negative Gibbs free energy (-ΔG).
Negative enthalpy, positive entropy:
Positive enthalpy and entropy with high temperature:
Negative enthalpy and entropy with low temperature:
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Which of the following scenarios describes a reaction in equilibrium?
Which of the following scenarios describes a reaction in equilibrium?
According to the Gibbs free energy equation, a system is at equilibrium when 
is equal to 0.
Since 
, a system is in equilibrium when 
. A negative Gibbs free energy means that the reaction will be spontaneous. At equilibrium, the forward reaction rate equals the reverse reaction rate, though the net rate is zero.
According to the Gibbs free energy equation, a system is at equilibrium when
Since
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When the enthalpy of a reaction has a value of 
, which word is used to describe the reaction?
When the enthalpy of a reaction has a value of
When the enthalpy of a reaction is negative, it means that heat has been released from the system to the surroundings. This release of energy is referred to as an exothermic reaction.
Endothermic reactions have a net heat flow into the system. Exergonic and endergonic are terms used to describe the change in free energy for a given system.
When the enthalpy of a reaction is negative, it means that heat has been released from the system to the surroundings. This release of energy is referred to as an exothermic reaction.
Endothermic reactions have a net heat flow into the system. Exergonic and endergonic are terms used to describe the change in free energy for a given system.
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