The value of standard free energy change `(DeltaG^(@))` of a redox reaction at a particular temperature may be calculated safely from measurnments of

Options

A. equilibrium constant of reaction
B. variation of rate constant with temperature
C. emf of approximate cell under standard conditions
D. standard enthalpy change of reaction.

Explanation

To solve the question regarding the calculation of the standard free energy change (ΔG°) of a redox reaction at a particular temperature, we can follow these steps:

### Step 1: Understand the Definition of ΔG°
- ΔG° (standard free energy change) is a thermodynamic quantity that indicates the spontaneity of a reaction under standard conditions (1 atm pressure, 1 M concentration, and a specified temperature, usually 25°C).

### Step 2: Identify the Relevant Equations
- There are two key equations that relate ΔG° to other thermodynamic quantities:
1. **Faraday's Equation**:
\[ ΔG° = -nFE° \]
where \( n \) is the number of moles of electrons transferred, \( F \) is Faraday's constant (approximately 96485 C/mol), and \( E° \) is the standard electromotive force (EMF) of the cell.

2. **Equilibrium Constant Relation**:
\[ ΔG° = -2.303RT \log K_{eq} \]
where \( R \) is the universal gas constant (8.314 J/(mol·K)), \( T \) is the temperature in Kelvin, and \( K_{eq} \) is the equilibrium constant of the reaction.

### Step 3: Analyze the Options Given in the Question
- The question asks from which measurements ΔG° can be calculated:
- **Option A**: Equilibrium constant of the reaction (True, as ΔG° can be calculated using the second equation).
- **Option B**: Variation of rate constant with temperature (False, as ΔG° does not directly relate to the rate constant).
- **Option C**: EMF of the approximate cell under standard conditions (True, as ΔG° can be calculated using the first equation).
- **Option D**: Standard enthalpy change of the reaction (False, as ΔG° is not directly calculated from enthalpy change).

### Step 4: Conclusion
- The correct measurements that can be used to calculate ΔG° are:
- The equilibrium constant of the reaction (Option A).
- The EMF of the approximate cell under standard conditions (Option C).

### Final Answer
The value of standard free energy change (ΔG°) of a redox reaction at a particular temperature may be calculated safely from:
1. The equilibrium constant of the reaction.
2. The EMF of the approximate cell under standard conditions.

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