Q19 of 23 Page 63

(a) Identify the compound of calcium which is yellowish white powder and is used for disinfecting drinking water. Write its chemical name and formula. How is it manufactured? Write the chemical equation for the reaction involved. Also list two other uses of the compound.

(b) Write the balanced chemical equation of chlor-alkali process.

a. The compound of calcium which is a yellowish white powder and is used for disinfecting drinking water is CaOCl2 commonly known as bleaching powder.

Its chemical name is – Calcium oxychloride


Formula - CaOCl2


The chemical equation for the reaction involved is: -


Ca(OH)2 + Cl2→ CaOCl2 + H2O


Two other uses of the compound are:-


1. It is used as an oxidising agent in many chemical industries.


2. It is used for bleaching cotton and linen in the textile industry, wood pulp bleaching and for bleaching washed clothes in the laundry.


b. The balanced chemical equation of chlor-alkali process is : -


2NaCl (aq) +2H2O (l) 2NaOH (aq) + Cl2 (g) + H2 (g)


More from this chapter

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17

In the following schematic diagram for the preparation of hydrogen gas as shown in the given 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.

 18

(a) Identify the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this slat. Name the source from where it is obtained.

(b) What is rock salt? Mention its colour and the reason due to which it has this colour.


(c) What happens when electricity is passed through brine? Write the chemical equation for it.

 20

(a) Crystals of a substance changed their colour on heating in a closed test tube but regained it after sometime when they were allowed to cool down. Name the substance and write its formula and explain the phenomenon involved.

(b) Name the compound whose one formula unit is associated with 10 water molecules. How is it prepared? Give equations of related reactions. Give two uses of the compound.

 21

Hritik tested rainwater and found a pH of 5-6 due to presence of H+ ions formed by reaction of rainwater with carbon dioxide. When pH of the rainwater drops below 5-6, then it is called acid rain. Oxides of nitrogen and sulphur are acidic in nature. Burning of fossil fuels such as coal and oil in power stations and furnace produce oxides of nitrogen and sulphur. He told all of his classmates living nearby to use bicycle instead of school bus so as to reduce air pollution and prevent acid rain.

(a) Which acid is formed by sulphur dioxide in presence of air?


(b) Which acid is formed by nitrogen dioxide in presence of air?


(c) Why is acid rain harmful for agriculture, trees and plants?


(d) How can we prevent from acid rain?


(e) What values are possessed by Hiritik?