Answer: Positive.
- A Negative
- B Positive
- C Zero
- D Temperature dependent
Correct answer: B. Positive
Explanation: Breaking bonds always requires energy input (endothermic), so bond dissociation enthalpy is always positive.
Isothermal expansion follows a gentler curve (heat flows in to keep T constant) while adiabatic expansion drops in pressure more steeply (no heat exchange, so internal energy and temperature fall as the gas does work).
Concept context
Study energy changes in chemical reactions. Understand enthalpy, entropy, Gibbs free energy, and the laws of thermodynamics that decide whether a reaction will occur spontaneously or not.