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CBSE Class 10 Science Exam 2014 Term 1 Paper

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Question : 20
Total: 36
Write balanced chemical equations for the following statements :
(i) NaOH solution is heated with zinc granules.
(ii) Excess of carbon dioxide gas is passed through lime water.
(iii) Dilute sulphuric acid reacts with sodium carbonate.
(iv) Egg shells are dropped in hydrochloric acid.
(v) Copper (II) oxide reacts with dilute hydrochloric acid.
Solution:  
(i)
2‌NaOH(aq)
Sodium Hydroxide
+
Zn
Zinc
(s)
Δ
──▶
Na2ZnO2(aq)
Sodium zincate
+
H2(g)
Hydrogen

(ii)
Ca(OH)2+
Lime water
CO2───▶
CaCO3( s)
Calcium carbonate (white ppt.)
+H2O
CaCO3( s)
Calcium carbonate
+CO2(g)+H2O(l)───▶
Ca(HCO3)(aq)
Calcium hydrogen carbonate (Soluble in water)
(iii) H2SO4 (dil.) +
Na2CO3(s)
Sodium carbonate
───▶
Na2SO4
Sodium sulphate
+CO2+H2O
(iv)
CaCO3( s)
Calcium carbonate
+2‌HCl
(v)
CuO( s)
Copper oxide
+2‌HCl(aq)→
CuCl2(aq)
Copper chloride
(blue green)
+H2O(l)
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