question_answer 40)

  Which of the following is(are) an endothermic process(es)? (i) Dilution of sulphuric add (ii) Sublimation of dry ice (iii) Condensation of water vapours (iv) Evaporation of water (a) Both (i) and (iii)          (b) Only (ii)                         (c) Only (iii)                         (d) Both (ii) and (iv)                

Answer:

  (d) Sublimation of dry ice and evaporation of water both are endothermic process and take heat (energy) from their surrounding to get sublime or evaporate. Hence, both these processes produce cooling. This is the reason for using dry ice as refrigerant. Dilution of sulphuric acid and condensation of water vapours evolve heat. Hence, these are exothermic processes.