What are exothermic and endothermic reactions?
Exothermic reactions are those reactions which are accompanied by the evolution of heat.
Endothermic reactions are those reactions which are accompanied by the absorption of heat.
State with reason whether the work is done by the system on the surroundings or on the system by the surroundings if the following change occurs at constant pressure:
What is the enthalpy of formation of the most stable form of an element in its standard state?