Q17 of 30 Page 1

Complete and balance the following chemical equations:

(i) NaOH(aq) + Zn(s)→


(ii) CaCO3(s) + H2O(l) + CO2(g)→


(iii) HCl(aq) + H2O(l)→


OR


During electrolysis of brine, a gas ‘G’ is liberated at anode. When this gas ‘G’ is passed through slaked lime, a compound ‘C’ is formed, which is used for disinfecting drinking water.


(i) Write formula of ‘G’ and ‘C’.


(ii) State the chemical equation involved.


(iii) What is common name of compound ‘C’? Give its chemical name.



CaCO3 + H2O → Ca(HCO3)2


HCl + H2O → H3O+ + Cl–


OR


(i) G is Cl2


C is CaOCl2


(ii) Cal(OH)2 + Cl2→ CaOCl2 + H2O


Calcium Chlorine Calcium oxy chloride Water


(iii) Bleaching Powder


Chemical name: Calcium chlorite.


Or


Calcium oxy-chloride.


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15

Identify 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.


 16

Study the data of the following three categories A, B and C.

(i) From the given three categories A, B and C, pick the one which forms Dobereiner’s Triads.


(ii) Why did Mendeleev laced elements of category A, B and C in three different groups?


(iii) Is Newland law of octaves applicable to all the three categories? Give reason to justify your answer.


 18

(a) State with reason the consequence of decrease in number of carnivores in an ecosystem.

(b) In a food chain, state the trophic level at which the concentration of harmful chemicals is maximum. Why is it so?


OR


How is ozone layer formed ? State its importance to all life forms on earth ? Why the amount of ozone in the atmosphere dropped sharply in the 1980s ?


 19

(a) State the role played by the following in the process of digestion.

(i) Enzyme trypsin


(ii) Enzyme lipase


(b) List two functions of finger like projections present in the small intestine.