The electron affinity of bromine (g) is 3.9 eV. How much energy in kJ is released when 10.0 g of bromine is converted completely to Br- in gaseous state?
[Given. Atomic mass of Br = 80, 1 eV = 96.3 kJ `"mol"^(-1)` ].

Explanation

To find out how much energy is released when 10.0 g of bromine (Br) is converted completely to Br⁻ in the gaseous state, we can follow these steps:

### Step 1: Determine the number of moles of bromine in 10.0 g
The atomic mass of bromine (Br) is given as 80 g/mol.

Using the formula for moles:
\[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]
Substituting the values:
\[ \text{Number of moles of Br} = \frac{10.0 \, \text{g}}{80 \, \text{g/mol}} = 0.125 \, \text{mol} \]

### Step 2: Calculate the energy released for 0.125 moles
The electron affinity of bromine is given as 3.9 eV. This means that when one mole of bromine atoms gains an electron, it releases 3.9 eV of energy.

To find the energy released for 0.125 moles:
\[ \text{Energy released (in eV)} = \text{Number of moles} \times \text{Electron affinity} \]
Substituting the values:
\[ \text{Energy released} = 0.125 \, \text{mol} \times 3.9 \, \text{eV} = 0.4875 \, \text{eV} \]

### Step 3: Convert energy from eV to kJ
We know that 1 eV = 96.3 kJ/mol. To convert the energy released from eV to kJ, we multiply by the conversion factor:
\[ \text{Energy released (in kJ)} = 0.4875 \, \text{eV} \times 96.3 \, \text{kJ/mol} \]
Calculating this gives:
\[ \text{Energy released} = 0.4875 \times 96.3 = 46.9 \, \text{kJ} \]

### Step 4: Include the sign for energy release
Since energy is released in the process, we denote this as a negative value:
\[ \text{Energy released} = -46.9 \, \text{kJ} \]

### Final Answer
The energy released when 10.0 g of bromine is converted completely to Br⁻ in the gaseous state is approximately **-46.9 kJ**.

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