Q23 of 26 Page 1

Aadik Behl was playing in the park with his friends. While running to catch a ball, one of his friends, Saurish fell down and he had a cut on his hand due to which lot of blood was coming out. Aadik took him to his house and applied alum on the cut due to which the blood stopped.

Answer the following questions:


(a) Why did the blood stop after applying alum on the cut?


(b) Alum is used for purification of water. Why?


(c) Artificial rain is caused by spraying silver iodide on clouds. Give reason.


(d) What are the values (any two) displayed by Aadik?


(a) Bleeding stops when blood clots which is coagulated blood protein. This blood proteins are charged particles, when they come in contact with Al3+ and SO42- ions present in alum they readily coagulate stopping the flow of blood. Alum acts as coagulant.


(b) When alum is added to water it reacts with the alkaline(especially bicarbonate) impurities to form a gelatinous precipitate. This gelatinous precipitate attracts other suspended impurities and settles at the bottom leaving water purified and colourless.


(c) Clouds are colloidal in nature and carry charge. Artificial rain occurs when oppositely charged clouds colloid. Silver iodide acts as a electrolyte which causes the coagulation of water particles resulting in rain.


(d) Aadik has a helpful and caring nature as he took care of his injured friend. He is sportive and friendly for he was playing with a group of friends.


More from this chapter

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21

(a) Identify the monomer in the following polymeric structure:


(b) Which one of the following is an Elastomer?


(c) On the basis of forces between their molecules in a polymer, to which class does polyester belong?


 22

Give one example for each of the following:

(a) An artificial sweetener whose use is limited to cold drinks.


(b) A non-ionic detergent.


(c) A pain reliever used for relief from severe pain like post-operative pain.


 24

Calculate the emf and for the following cell at 298K:


OR


(a) Give reasons for the following:


(i) Iron does not rust even if zinc coating is broken in galvanized pipe.


(ii) Copper sulphate solution cannot be stored in zinc container.


(b) The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1S cm2mol-1. Calculate its degree of dissociation and dissociation constant.


[Given: λoH+ = 349.6 S cm2 mol-1 ; λoHCOO- = 54.6 S cm2 mol-1]


 25

(a) Why do actinoids show a wide range of oxidation states? Write one similarity between the chemistry of lanthanoids and actinoids.

(b) Second I.E. of chromium and copper are exceptionally higher than that of their neighbouring elements. Explain.


(c) Zinc has lowest energy of atomization in 3d-series. Why?


OR


(a) Give reasons for the following:


(i) Transition metals are paramagnetic.


(ii) Transition metals show variable oxidation states.


(iii) Zr and Hf have nearly similar atomic radii.


(b) Write the preparation of KMnO4 from pyrolusite ore(MnO2).