On adding a white solid ‘X’ to water, a hissing sound is heard and a lot of heat is produced along with the formation a product ‘Y’.
The solution of ‘Y’ is applied on the walls of buildings during whitewashing. It reacts with carbon dioxide in air to form 'Z'. This Z gives a shiny finishing to the walls after 2-3 days of whitewashing.

(i) The chemical formula of solid ‘X’ is _______.

MgO

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CaCO₃

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CaO

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Ca(OH)₂

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Solution

The correct option is C CaO
The white solid 'X' is calcium oxide with chemical formula CaO and is commonly known as quicklime. Calcium oxide reacts with water to form calcium hydroxide(slaked lime) and a lot of heat is also released. The reaction can be represented as:
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat

Solution of slaked lime is used for whitewashing of the walls.

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Similar questions

Q. On adding a white solid ‘X’ to water, a hissing sound is heard and a lot of heat is produced along with the formation a product ‘Y’.
The solution of ‘Y’ is applied on the walls of buildings during whitewashing. It reacts with carbon dioxide in air to form 'Z'. This Z gives a shiny finishing to the walls after 2-3 days of whitewashing.

(ii) The chemical formula of the product Y is _______.

Q. On adding a white solid ‘X’ to water, a hissing sound is heard and a lot of heat is produced along with the formation a product ‘Y’.
The solution of ‘Y’ is applied on the walls of buildings during whitewashing. It reacts with carbon dioxide in air to form 'Z'. This Z gives a shiny finishing to the walls after 2-3 days of whitewashing.

(iii) Formation of Y in this case is an example of _________ reaction.

Q. When water is added gradually to a white solid X, a hissing sound is heard and a lot of heat is produced forming a product Y. A suspension of Y in water is applied to the walls of a house during white washing. A clear solution of Y is also used for testing carbon dioxide gas in the laboratory.
(a) What could be solid X? Write its chemical formula.
(b) What could be product Y? Write its chemical formula.
(c) What is the common name of the solution of Y which is used for testing carbon dioxide gas?
(d) Write chemical equation of the reaction which takes place on adding water to slid X.
(e) Which characteristic of chemical reactions is illustrated by this example?

Q. Why whitewashing walls gives a shiny finish to the walls?

We use a solution of slaked lime to whitewash the walls. In the beginning the wall looks rough and coarse, but after 2 - 3 days the wall appears smooth and shiny. This is due to the formation of:

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