Question

Energy required to dissociate \(16\,\text{g}\) of \(\text{O}_2(g)\) into free atoms is \(x\,\text{kJ}\). The value of bond enthalpy of \(\text{O}=\text{O}\) bond is

• A. \(2x\,\text{kJ}\)
• B. \(\dfrac{x}{2}\,\text{kJ}\)
• C. \(4x\,\text{kJ}\)
• D. \(16x\,\text{kJ}\)

Hint:

Bond enthalpy is always defined per mole of bonds broken.

Answer 1

The Correct Option is A

Step 1: Convert mass into moles.
Molar mass of \(\text{O}_2 = 32\,\text{g mol}^{-1}\).
\[ 16\,\text{g of } \text{O}_2 = \frac{16}{32} = 0.5\,\text{mol} \] Step 2: Interpret given energy.
Energy \(x\,\text{kJ}\) is required to break \(0.5\) mol of \(\text{O}=\text{O}\) bonds.
Step 3: Calculate bond enthalpy.
Energy required to break \(1\) mol of \(\text{O}=\text{O}\) bonds is: \[ \frac{x}{0.5} = 2x\,\text{kJ} \] Step 4: Conclusion.
Thus, bond enthalpy of \(\text{O}=\text{O}\) bond is \(2x\,\text{kJ}\).