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प्रश्न
Define exothermic and endothermic changes. Give two example in each case.
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उत्तर
Exothermic Reaction
The chemical reactions which proceed with the evolution of heat energy are called exothermic reactions.
Examples:
Carbon burns in oxygen to form carbon dioxide and heat energy is produced.
C + O2 → CO2 + Heat
Water added to quick lime (calcium oxide), slaked lime (calcium hydroxide) is produced with a lot of heat energy.
CaO + H2O → Ca(OH)2 + Heat
Endothermic Reaction
The chemical reactions which proceed with the absorption of heat energy are called as endothermic reactions.
Examples:
When nitrogen and oxygen are heated together to a particular temperature of about 3000oC, nitric oxide gas is formed.
N2 + O2 + Heat → 2NO
Calcium carbonate decomposes into carbon dioxide and calcium oxide when heated to a temperature of about 1000oC.
CaCO3 + Heat → CaO + CO2
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संबंधित प्रश्न
Give scientific reasons.
While preparing dil. Sulphuric acid from concentrated conc. sulphuric acid in the laboratory the concentrated sulphuric acid is, add slowly to water with constant stirring.
Name a carbonate which do not decompose on heating.
Chemical reactions may proceed with evolution of heat. Give an example.
Chemical reactions may proceed with absorption of heat. Give an example.
Supply of energy may be required to initiate a reaction. State the different forms with a suitable example of reactions initiated by the supply of energy.
True or False. If false, give the correct answer.
Tarnishing of silver is an example of endothermic change.
Assertion: A drop of petrol when touched with finger gives a chill feeling.
Reason: The above phenomenon is an endothermic one.
Complete the following table:
| Chemical Reactions | Name reaction type |
| \[\ce{C(s) + O2(g) -> CO2(g)}\] | (a) ________ |
| \[\ce{Zn(s) + CuSO4(aq) ->}\] (b) _________ | Displacement reaction |
| \[\ce{2Cu(s) + O2(g) ->[heat] 2CuO(s)}\] | (c) _________ |
| \[\ce{C(s) + 2H2(g) -> CH4(g)}\] | (d) _________ |
| \[\ce{CaO(s) + H2O(l) -> Ca(OH)2(aq) + heat}\] | (e) _________ |
| \[\ce{CaCO3(s) + Heat ->}\] (f) _________ | Endothermic Reaction |
Give a scientific reason.
While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring.
Give scientific reason.
While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring.
