The entropy change for a phase transformation is :

Options

A. `(DeltaU)/(gamma+dT)`
B. `(DeltaT)/(DeltaH)`
C. `(DeltaH)/(T)`
D. `(DeltaH+DeltaG)/(T)`

Explanation

To solve the question regarding the entropy change for a phase transformation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Phase Transformation**:
- A phase transformation occurs when a substance changes from one state of matter to another, such as solid to liquid (melting), liquid to gas (vaporization), or solid to gas (sublimation).

2. **Equilibrium Condition**:
- During a phase transformation, the system is at equilibrium. This means that the temperature remains constant throughout the process.

3. **Gibbs Free Energy**:
- At equilibrium, the change in Gibbs free energy (ΔG) is equal to zero (ΔG = 0). This is a key point in understanding the relationship between enthalpy, entropy, and temperature.

4. **Gibbs Free Energy Equation**:
- The Gibbs free energy can be expressed as:
\[ \Delta G = \Delta H - T \Delta S \]
where:
- ΔG = change in Gibbs free energy
- ΔH = change in enthalpy
- T = absolute temperature
- ΔS = change in entropy

5. **Setting ΔG to Zero**:
- Since ΔG = 0 at equilibrium, we can rearrange the equation:
\[ 0 = \Delta H - T \Delta S \]
This leads to:
\[ T \Delta S = \Delta H \]

6. **Solving for Entropy Change**:
- From the above equation, we can solve for the change in entropy (ΔS):
\[ \Delta S = \frac{\Delta H}{T} \]
This equation shows that the change in entropy during a phase transformation is equal to the change in enthalpy divided by the temperature.

### Conclusion:
The entropy change for a phase transformation can be expressed as:
\[ \Delta S = \frac{\Delta H}{T} \]