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CBSE Class 10 Science 2023 Delhi Set 1

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Question : 21 of 39
Marks: +1, -0
(A) A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution.
(i). Write the name of the compound formed and its colour.
(ii) Write a balanced chemical equation for the reaction involved.
OR
(B) The industial process used for the manufacture of caustic soda involves electrolysis of an aqueous solution of compound ' XX '. In this process, two gases ' YY ' and ' ZZ ' are liberated. ' YY ' is liberated at cathode and ' ZZ ', which is liberated at anode, on treatment with dry slaked lime forms a compound ' BB '. Name X,YX, Y, ZZ and BB .
Solution:  
(A) (i) The compound is copper (II) chloride (CuCl2)(\mathrm{CuCl}_2) and it is bluish in colour.
(ii) CuO(s)+2HCl(aq)→CuCl2(aq)+H2O(l)\mathrm{CuO}(\mathrm{s}) + 2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{CuCl}_2(\mathrm{aq}) + \mathrm{H}_2\mathrm{O}(\mathrm{l})
OR
(B)
  X=NaCl   (Sodium chloride); \; X = \mathrm{NaCl} \; \text{ (Sodium chloride); }
  Y=H2   (Hydrogen gas); \; Y = \mathrm{H}_2 \; \text{ (Hydrogen gas); }
  Z=Cl2   (Chlorine gas); \; Z = \mathrm{Cl}_2 \; \text{ (Chlorine gas); }
  B=Bleaching   powder   (CaOCl2).\; B = \text{Bleaching} \; \text{ powder } \; (\mathrm{CaOCl}_2).
  2NaCl(aq)+2H2O(l)→2NaOH(aq)    +Cl2(g)+H2(g)\;2 \mathrm{NaCl}(\mathrm{aq}) + 2 \mathrm{H}_2\mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}_{(\mathrm{aq})} \; \; + \mathrm{Cl}_2(\mathrm{g}) + \mathrm{H}_2(\mathrm{g})
      Ca(OH)2+Cl2→CaOCl2+H2O\; \; \; \mathrm{Ca}(\mathrm{OH})_2 + \mathrm{Cl}_2 \rightarrow \mathrm{CaOCl}_2 + \mathrm{H}_2\mathrm{O}
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