Question

For a spontaneous process, the value of Gibbs energy change (\(\Delta G\)) is always:

• A. Positive
• B. Negative
• C. Zero
• D. Infinity

Hint:

Remember the Gibbs free energy rule: \[ \Delta G < 0 \Rightarrow \text{Spontaneous} \] \[ \Delta G = 0 \Rightarrow \text{Equilibrium} \] \[ \Delta G > 0 \Rightarrow \text{Non-spontaneous} \]

Answer 1

The Correct Option is B

Concept: The spontaneity of a process is determined using Gibbs free energy. The Gibbs free energy equation is \[ \Delta G = \Delta H - T\Delta S \] where
• \(\Delta G\) = Gibbs free energy change
• \(\Delta H\) = Enthalpy change
• \(T\) = Absolute temperature
• \(\Delta S\) = Entropy change The sign of \(\Delta G\) determines whether a process can occur spontaneously under given conditions.

Step 1: Recall the criterion for spontaneity
For a process to occur on its own without continuous external assistance, it must be thermodynamically favorable. The condition is \[ \Delta G < 0 \] This means the Gibbs free energy of the system decreases during the process. Such a process is called spontaneous.

Step 2: Understand the significance of different values of \(\Delta G\)
Case 1: \[ \Delta G < 0 \] The process is spontaneous. Case 2: \[ \Delta G > 0 \] The process is non-spontaneous and requires external energy. Case 3: \[ \Delta G = 0 \] The system is at equilibrium. No net change occurs.

Step 3: Compare with the given options
Option (A): Positive \[ \Delta G > 0 \] Non-spontaneous. Incorrect. Option (B): Negative \[ \Delta G < 0 \] Spontaneous. Correct. Option (C): Zero Represents equilibrium. Incorrect. Option (D): Infinity Not a thermodynamic criterion for spontaneity. Incorrect. Final Conclusion: For every spontaneous process, \[ \boxed{\Delta G < 0} \] Therefore, the correct answer is \[ \boxed{(B)\ \text{Negative}} \]