Q35 of 152 Page 20

What do you understand by exothermic and endothermic reactions?

Heat evolving reaction are known as exothermic reactions. In these reactions Heat is released when reaction starts. The energy needed to initiate the reaction is less than the energy needed given from the reaction.

In reaction where heat is absorbed are known as endothermic. The heat energy is gained from the atmosphere in this reaction. The heat required to initiate the reaction is fairly high than the heat given from the reaction.



More from this chapter

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34 State the various characteristics of chemical reactions. 34 State one characteristic each of the chemical reaction which takes place when:

(i) dilute hydrochloric acid is added to sodium carbonate


(ii) lemon juice is added gradually to potassium permanganate solution


(iii) dilute sulphuric acid is added to barium chloride solution


(iv) quicklime is treated with water


(v) wax is burned in the form of a candle

 35 Give one example of an exothermic reaction and one of an endothermic reaction. 35 Which of the following are endothermic reactions and which are exothermic reactions ?

(i) Burning of natural gas


(ii) Photosynthesis


(iii) Electrolysis of water


(iv) Respiration


(v) Decomposition of calcium carbonate