Que. what is endothermic and exothermic reactions? and what is meant by the + Q Kcal or +Q KJ and - Q Kacl or - Q KJ?
Endothermic reactions – Reactions which absorb energy as they take place are called endothermic reactions.Example:
N2(g) + O2(g) + heat → 2NO(g)
Exothermic reactions – Reactions which evolve energy as they take place are called exothermic reactions.Example:
C(s) + O2(g) → CO2(g) + heat
The amount of heat absorbed or released is represented as Q and units of heat may be Kcal or KJ. (+) sign indicates heat is absorbed while (–) sign indicates heat is released.