Choose the Incorrect Statement: 1 For a system at equilibrium, chemical potential is same in all phases.
2 Gibb's free energy change is zero at equilibrium state of a system.
3 Gibb's free energy change is positive for reaction to occur spontaneously.
4 $\Delta G$ will become more negative with increasing temperature.
Identifying the Incorrect Statement
This question requires identifying the false statement concerning chemical equilibrium and Gibbs free energy ($\Delta G$). Let's evaluate each statement:
1. Chemical Potential at Equilibrium
A system is at equilibrium when the chemical potential ($\mu$) of a species is the same in all accessible phases. This statement is correct.
2. Gibbs Free Energy Change at Equilibrium
At equilibrium, the Gibbs free energy ($G$) of the system is minimized. Consequently, the change in Gibbs free energy ($\Delta G$) for any process occurring at equilibrium is zero. This statement is correct.
Condition: $\Delta G = 0$
3. Spontaneity and Positive $\Delta G$
The criterion for a spontaneous process is a negative Gibbs free energy change ($\Delta G$). A positive $\Delta G$ indicates that the process is non-spontaneous under the given conditions.
- Spontaneous: $\Delta G < 0$
- Equilibrium: $\Delta G = 0$
- Non-spontaneous: $\Delta G > 0$
Therefore, the statement 'Gibb's free energy change is positive for reaction to occur spontaneously' is incorrect.
4. Temperature Dependence of $\Delta G$
The relationship is $\Delta G = \Delta H - T \Delta S$. The change in $\Delta G$ with temperature ($T$) depends on the sign of the entropy change ($\Delta S$). If $\Delta S > 0$, $\Delta G$ becomes more negative with increasing $T$. If $\Delta S < 0$, $\Delta G$ becomes less negative (or more positive). This statement is not universally true and depends on $\Delta S$. However, statement 3 is definitionally incorrect.
The definitively incorrect statement is number 3.
Important Questions from Thermodynamics
- Second law of thermodynamics states that
A. Energy flows from higher concentration to lower concentration.
B. Order becomes disorder during energy transformations.
C. The quality of energy degrades as it is transformed.
D. Degraded energy is entropy, dessipated as waste products or heat.
E. Enthalpy is wasted in energy transformation.
Choose the most appropriate answer from the options given below: - In a closed thermodynamic system, across its boundaries
Melting Point of pure ice is-
Which one among the following statements with reference to the properties of water is not correct?
For a certain reaction, ΔG θ = -45 kJ/mol and ΔH θ = -90 kJ/mol at 0 °C. What is the minimum temperature at which the reaction will become spontaneous, assuming that ΔH θ and ΔS θ are independent of temperature?
