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CBSE Class 10 Science 2020 Outside Delhi Set 3

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Question : 1 of 6
Marks: +1, -0
Identity the type of each of the following reactions. Also write balanced chemical equation for each reaction.
(i) A reaction in which the reaction mixture becomes warm.
(ii) A reaction in which an insoluble substance is formed
Solution:  
(i) Reactions in which the reaction mixture becomes warm and heat is released along with the formation of products are called exothermic reactions. Example of exothermic reactions :
Burning of natural gas
CH4(g)+2O2(g)→  CO2(g)+2H2O(g)CaO  +H2O→Ca(OH)2\mathrm{CH}_4(\mathrm{g}) + 2\mathrm{O}_2(\mathrm{g}) \rightarrow\; \mathrm{CO}_2(\mathrm{g}) + 2\mathrm{H}_2\mathrm{O}(\mathrm{g}) \quad \mathrm{CaO}\; + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_2
(ii) Reactions in which an insoluble substance is formed is known as precipitation reaction. For example: Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
Na2SO4(aq)(Sodiumsulphate)+BaCl2(aq)(Barium chloride)→BaSO4(s)(Barium sulphate)+2NaCl(aq)(Sodium chloride)\underset{\text{(Sodiumsulphate)}}{\mathrm{Na_2SO_4(aq)}} + \underset{\text{(Barium chloride)}}{\mathrm{BaCl_2(aq)}} \rightarrow \underset{\text{(Barium sulphate)}}{\mathrm{BaSO_4(s)}} + \underset{\text{(Sodium chloride)}}{2\mathrm{NaCl(aq)}}
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