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7. ATOMS, MOLECULES AND, CHEMICAL REACTIONS, Reflections on concepts, , 10. Write an equation for decomposition reaction where energy is supplied in the form of, Heat / light / electricity., ANS:, , 11. How chemical displacement reactions differ from chemical decomposition reaction?, Explain with an example for each., ANS: In chemical displacement reaction, one element displaces another element whereas in chemical, decomposition reaction, the compound decomposes or breaks into more elements or Compounds., , 12. Name the reactions taking place in the presence of sunlight?, ANS: The reaction that takes place in the presence of sunlight is called photochemical reaction.
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13. Give two examples for oxidation-reduction reaction., ANS:, , Application of concepts, , 1. Why do we apply paint on iron articles?, ANS;, When iron is exposed to air and water then it reacts terribly and ends up with rusting of iron., However, iron articles are painted off so that iron won’t be able to react with the air and water., It is a way to prevent the reaction that will simultaneously stop the rusting of iron., , 2. What is the use of keeping food in air tight containers?, ANS;, Keeping food in air tight containers helps against rancidity., When oxygen molecules come in contact with other substances from metals to tissues, they, oxidize., So, when fats and oil oxidize, they become rancid which changes their smell and taste., Since the food is completely sealed, we can store it for a log time without spoiling., Food remains fresh in containers without losing its moisture to air., , 1. Fe2 O3 + 2Al → Al2 O3 + 2 Fe., The above reaction is an example of:, a) Combination reaction, b) Decomposition reaction, c) Displacement reaction, d) Double decomposition reaction, 2. What happens when dil. hydrochloric acid is added to iron filings?, Choose the correct answer., a) Hydrogen gas and iron chloride are produced., b) Chlorine gas and iron hydroxide are produced., c) No reaction takes place., d) Iron salt and water are produced., , [ C, , ], , [ A, , ]
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3. 2 PbO(s) + C (s) → 2Pb(s) + CO2 (g), [ D, Which of the following statements are correct for the above chemical reaction?, a) Lead oxide is reduced, b) Carbon dioxide is oxidized, c) Carbon is oxidized, d) (a) and (c) are correct, , ], , 4. The chemical equation BaCl 2 + Na2 SO4 → BaSO4 + 2NaCl represents following type of chemical, reaction., [ IV, ], i) displacement, ii) combination, iii) decomposition, iv) double-displacement, 5. The reaction of formation hydrogen chloride from hydrogen and chloride represents following type of, chemical reaction, [III, ], i) decomposition, ii) displacement, iii) combination, iv) double-displacement
