Question

Appropriate chemical equation of each
(A) A green hydrated metallic salt on heating loses water of crystallization and gives a gas with a suffocating smell. Identify the salt and type of the reaction. Give the chemical equation.
(B) A shiny reddish brown coloured substance “X” on heating in air forms a black substance “Y”. When hydrogen gas is passed over heated “Y”, it again changes back into “X”.
Identify the substance X and Y
Give the chemical equations for both the reactions
(C) A white salt on heat decomposes to give brown fumes and a yellow residue is left behind. Name the salt and write the decomposition reaction.

Answer 1

Hint :Let us consider green colour hydrated metallic salt can be Ferrous sulphate reddish brown colour substance can be copper $ (X) $
$ 2{{(PbN{{O}_{3}})}_{2}}\to 2PbO+4N{{O}_{2}}+{{O}_{2}} $
White salt can be Lead nitrate.

Complete Step By Step Answer:
The answer for the first question
Ferrous sulphate on heating gives pungent smell of sulphur
 $ 2FeS{{O}_{4}}+Heat\to F{{e}_{2}}{{O}_{3}}+S{{O}_{2}}+S{{O}_{3}} $ $ 2FeS{{O}_{4}}+Heat\to F{{e}_{2}}{{O}_{3}}+S{{O}_{2}}+S{{O}_{3}} $
Ferrous sulphate on heating gives Sulphur dioxide and Sulphur trioxide which is the reason for pungent smell
Ferrous sulphate on heating loses water and forms anhydrous ferrous sulphate
Anhydrous ferrous sulphate further decomposes to form ferric oxide, sodium di oxide and sodium trioxide
Decomposition of ferrous sulphate is an endothermic reaction because heat is absorbed during the reaction
The answer for the second question
Shiny reddish brown colour substance can be considered as Copper $ (X) $
 $ 2Cu(X)+{{O}_{2}}\to 2CuO(Y) $
 $ CuO $ on heating with hydrogen gas forms water and copper
 $ CuO(Y)+{{H}_{2}}\to Cu(X)+{{H}_{2}}O $
Copper reacts with oxygen to form copper oxide
Copper oxide on heating with hydrogen gas forms copper and water
Therefore, the substance X and Y are Copper and Copper oxide
The chemical reaction for X is $ 2Cu(X)+{{O}_{2}}\to 2CuO(Y) $
The chemical reaction for Y is $ CuO(Y)+{{H}_{2}}\to Cu(X)+{{H}_{2}}O $
The answer for the third question
The chemical name of the white salt is lead nitrate
Lead nitrate molecular formula is $ {{(PbN{{O}_{3}})}_{2}} $
 $ 2{{(PbN{{O}_{3}})}_{2}}\to 2PbO+4N{{O}_{2}}+{{O}_{2}} $
Lead nitrate on heating gives lead oxide, nitrogen dioxide and oxygen
Lead nitrate is a colourless solution which on heating gives lead oxide which is a yellow residue and nitrogen dioxide which is responsible for brown fumes
The salt name is lead nitrate
The chemical equation is $ 2{{(PbN{{O}_{3}})}_{2}}\to 2PbO+4N{{O}_{2}}+{{O}_{2}} $ .

Note :
 $ 2FeS{{O}_{4}}+Heat\to F{{e}_{2}}{{O}_{3}}+S{{O}_{2}}+S{{O}_{3}} $ is the chemical equation for the first question
 $ 2Cu(X)+{{O}_{2}}\to 2CuO(Y) $
 $ CuO(Y)+{{H}_{2}}\to Cu(X)+{{H}_{2}}O $ is the chemical equation for the second question
 $ 2{{(PbN{{O}_{3}})}_{2}}\to 2PbO+4N{{O}_{2}}+{{O}_{2}} $ is the chemical equation for the third question.