The absolute value of which of the following cannot be determined?

Options

A. EMF of the cell
B. Quantity of electricity
C. Single electrode potential
D. Free energy change

Answer

To determine which of the following cannot have its absolute value calculated, we will analyze each option provided:

1. **EMF of the Cell**: The electromotive force (EMF) of a cell can be measured and calculated using the Nernst equation or from standard electrode potentials. Therefore, the absolute value of EMF can be determined.

2. **Quantity of Electricity**: The quantity of electricity can be calculated using the formula \( Q = I \times t \), where \( Q \) is the quantity of electricity, \( I \) is the current, and \( t \) is the time. Thus, the absolute value of the quantity of electricity can also be determined.

3. **Single Electrode Potential**: The single electrode potential refers to the potential of a half-cell reaction. However, it cannot be measured independently because it is always relative to another half-cell. Therefore, we can only determine the difference in potential between two electrodes, not the absolute value of a single electrode potential.

4. **Free Energy Change**: The free energy change (\( \Delta G \)) can be calculated using the relationship \( \Delta G = -nFE \), where \( n \) is the number of moles of electrons transferred, \( F \) is Faraday's constant, and \( E \) is the EMF of the cell. Thus, the absolute value of free energy change can be determined.

Based on this analysis, we conclude that the absolute value that cannot be determined is:

**Answer**: Single Electrode Potential (Option 3).