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.

displacement

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decomposition

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combination

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redox

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Solution

The correct option is C combination
If two or more reactants combine to form a single product then the reaction is called as combination reaction. The general representation of this reaction is given below:
$A+B \to AB$

Calcium oxide on reacting with water forms calcium hydroxide(Y) according to the given reaction:
$CaO(s)$ + $H_{2} O(l) \to$ ${Ca(OH)}_{2} (a q)$ + Heat

So, the formation of Y here in this case is an example of combination reaction.

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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.

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

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

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?

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:

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

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