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)

Answer 1

Answer:

The answer of the given question is (a) i and ii

Explanation:

• The "reaction of water" with quick lime forms calcium hydroxide and "releases a lot of heat" energy, so it is exothermic reaction.
• Dilution of acid by adding water to concentrated acid releases a lot of heat energy, so it is exothermic reaction.
• Evaporation of water is an "endothermic reaction" because the water molecules absorb heat energy to get vaporized.
• Sublimation of camphor is an endothermic reaction because camphor absorbs heat energy to get vaporized.

Answer 2

Answer:

Option (a) (i) and (ii) include exothermic processes.

Explanation:

• In Thermochemistry, an exothermic reaction is most often spelt as a chemical reaction involving the release of energy in the form of light or heat.

• Thus in such a reaction, the energy is transferred outside which means to the surroundings. Hence ΔH (change in enthalpy)= -ve.

• When water reacts with quicklime, it results in calcium hydroxide($CaOH_{2}$) with the release of heat.

(1) Reaction of water with quick lime:

(Calcium oxide) $CaO + H_{2} O$ → $Ca(OH)_{2}$ (calcium hydroxide) + heat↑

• Hence it is an exothermic reaction.

• The process of dilution of concentrated acid is highly energy-releasing.

(2) Dilution of acid:

(Sulphuric Acid) +  $H_{2} O$ → $H_{3} O^{+}$+ $H_{2} SO_{4} ^{-}$ + heat↑

• Evaporation of water and sublimation of camphor are examples of cooling processes i.e energy-requiring endothermic reactions.
• Here ΔH (change in enthalpy)= +ve.

Therefore, the Reactions of water with quick lime and Dilution of acid are energy-releasing exothermic processes.

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