A student compares two endothermic processes carried out at 1 atm
CHEMISTRY · Single correct · CBSE · Chemistry · Is Matter Around Us Pure? · Is Matter Around Us Pure?
Problem
A student compares two endothermic processes carried out at 1 atm.
• Sublimation of CO₂(s): 25.9 kJ mol⁻¹
• Thermal decomposition of CaCO₃(s): 178 kJ mol⁻¹
Based on the magnitude of the enthalpy changes, which of the following classifications is most consistent with these data?
(a) Both processes are chemical changes because the enthalpy change is positive and solid bonds must be broken.
(b) Both processes are physical changes because each simply converts solid matter directly into gas while absorbing heat.
(c) Sublimation is a physical change and decomposition is a chemical change because the latter requires significantly more energy per mole.
(d) Sublimation is a chemical change because a new gaseous species forms, whereas decomposition is physical because it only releases the CO₂ already present.