When the first electron gain enthalpy `(triangle_(eg)H)` of oxygen is `-141 kJ//mol,` its second electron gain enthalpy is :

Options

A. a more negative value than the first
B. almost the same as that of the first
C. negative, but less negative than the first
D. a positive value

Answer

To determine the second electron gain enthalpy of oxygen given that the first electron gain enthalpy is -141 kJ/mol, we can follow these steps:

### Step 1: Understand Electron Gain Enthalpy
Electron gain enthalpy is the energy change when an electron is added to a neutral atom in the gas phase. The first electron gain enthalpy of oxygen is given as -141 kJ/mol, which means energy is released when an electron is added to a neutral oxygen atom to form O⁻.

**Hint:** Remember that a negative value indicates that energy is released when the electron is added.

### Step 2: Consider the Second Electron Gain Enthalpy
When we add a second electron to the O⁻ ion to form O²⁻, we need to consider the nature of the charges involved. The O⁻ ion is already negatively charged, and the electron we want to add is also negatively charged.

**Hint:** Think about the interaction between like charges. What happens when you try to bring two negatively charged particles close together?

### Step 3: Analyze the Energy Requirement
Since both the O⁻ ion and the incoming electron are negatively charged, they will repel each other. This means that energy must be supplied to overcome this repulsion in order to add the second electron. Therefore, the second electron gain enthalpy will be positive, indicating that energy is required to add the electron.

**Hint:** If energy is required to add the second electron, what does that tell you about the sign of the second electron gain enthalpy?

### Step 4: Conclusion
Given that the first electron gain enthalpy is -141 kJ/mol, the second electron gain enthalpy will be a positive value, indicating that energy is absorbed. This value will be significantly larger than the first electron gain enthalpy because of the increased repulsion.

**Final Answer:** The second electron gain enthalpy of oxygen is positive and significantly larger than -141 kJ/mol.

### Summary of Steps:
1. Understand the concept of electron gain enthalpy.
2. Consider the charges involved when adding a second electron.
3. Analyze the energy requirement due to charge repulsion.
4. Conclude that the second electron gain enthalpy is positive.