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) (iii) and (iv)Chemical Reactionsand Equations1CHAPTER07/05/2018
Question
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) (iii) and (iv)Chemical Reactionsand Equations1CHAPTER07/05/2018
Solution
An exothermic process is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic process.
(i) Reaction of water with quick lime is an exothermic process. In this process, heat is released when quicklime (calcium oxide) reacts with water to form slaked lime (calcium hydroxide).
(ii) Dilution of an acid is also an exothermic process. When an acid is diluted, the water molecules decrease the concentration of hydrogen ions present in the acid solution. This process releases heat.
(iii) Evaporation of water is an endothermic process, not exothermic. It requires heat to change water from a liquid to a gas.
(iv) Sublimation of camphor (crystals) is also an endothermic process. Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. This process absorbs heat from the surroundings.
So, the correct answer is (a) (i) and (ii).
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