Which of the following are exothermic processes? (i) Reaction of water with quick lime (ii) Dilution of an acid (iii) Evaporation of water (iv) Sublimation of camphor (crystals) (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (ii) and (iv)
Answer: (i) Reaction of water with quicklime (ii) Dilution of an acid Exothermic reactions are chemical reactions that release energy as heat or light. A large amount of heat is released when quick lime reacts with water, along with the formation of calcium hydroxide. Similarly, the process of dissolving an acid or base in water is a highly exothermic reaction. Water should never be added to acid, but the acid can be added to water for dilution. Evaporation of water and sublimation of camphor are endothermic reactions. Exothermic Reaction An exothermic reaction is a reaction in which energy is released in the form of light or heat. Thus in an exothermic reaction, energy is transferred into the surroundings rather than taking energy from the surroundings as in an endothermic reaction. In an exothermic reaction, change in enthalpy ( ΔH) will be negative.
