For a system in equilibrium, `DeltaG=0`, under conditions of constant

Options

A. Temperature and pressure
B. Temperature and volume
C. Pressure and volume
D. Energy and volume

Explanation

To solve the question regarding the conditions under which the Gibbs free energy change (ΔG) equals zero for a system in equilibrium, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding ΔG in Equilibrium**:
- For a system in equilibrium, the change in Gibbs free energy (ΔG) is equal to zero. This indicates that the system is at a state where no net change occurs.

2. **Gibbs Free Energy Equation**:
- The Gibbs free energy change can be expressed as:
\[ \Delta G = \Delta H - T \Delta S \]
- Here, ΔH is the change in enthalpy, T is the temperature, and ΔS is the change in entropy.

3. **Conditions for ΔG = 0**:
- When ΔG = 0, it implies that the system is at equilibrium. This condition typically occurs under constant temperature and pressure.

4. **Relation to Equilibrium Constant**:
- The relationship between ΔG and the equilibrium constant (K) is given by:
\[ \Delta G = \Delta G^\circ + RT \ln K \]
- At equilibrium, ΔG = 0, which leads to:
\[ 0 = \Delta G^\circ + RT \ln K \]
- This indicates that ΔG° is related to the equilibrium constant under standard conditions.

5. **Conclusion**:
- Therefore, for ΔG to be zero in a system at equilibrium, the conditions must be constant temperature and pressure.

### Final Answer:
The correct answer is: **Temperature and Pressure**.