Q45 of 48 Page 16

A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G , and Z.

X is calcium carbonate. When calcium carbonate reacts with acid such as hydrochloric acid, carbon dioxide is released.



Solution Y is lime water [Ca(OH)2 ]. When CO2 is passing through lime water, it turns milky due to the formation of calcium carbonate.



During electrolysis of brine, chlorine (G) gas is deposited at anode.



When chlorine gas is passed through dry slaked lime Ca(OH)2 (Y), it produces bleaching powder (Z). Bleaching powder is used for disinfecting drinking water.


Ca(OH) + Cl2 CaOCl2 + H2O



Hence, Z is calcium oxychloride (CaOCl2) or bleaching powder.


To sum up,


1. Metal carbonate (X) is calcium carbonate.


2. Solution (Y) is lime water (calcium hydroxide).


3. Gas (G) is chlorine gas.


4. Dry (Y) is dry calcium hydroxide (dry slaked lime).


5. Compound (Z) is bleaching powder (calcium oxychloride).


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43

In the following schematic diagram for the preparation of hydrogen gas as shown in the figure, what would happen if the following changes are made?



(a) In place of zinc granules, same amount of zinc dust is taken in the test tube.


(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.


(c) In place of zinc, copper turnings are taken.


(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

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(a) How will it affect the taste of the cake and why?


(b) How can baking soda be converted into baking powder?


(c) What is the role of tartaric acid added to baking soda?

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