Question

The enthalpies of combustion of \( H_2 \), \( C \) (graphite) and \( C_2H_6 (g) \) are \( -286.0,\; -394.0 \) and \( -1560.0 \, kJ \, mol^{-1} \) at \( 25^\circ C \) and 1 atm pressure. The enthalpy of formation of ethane is :

• A. \( -97.0 \, kJ \, mol^{-1} \)
• B. \( -86.0 \, kJ \, mol^{-1} \)
• C. \( -92.0 \, kJ \, mol^{-1} \)
• D. \( -78.0 \, kJ \, mol^{-1} \)

Hint:

Use Hess law carefullyAlways convert combustion data into formation reaction by reversing and adding equations properly.

Answer 1

The Correct Option is B