Question

A chemical is heated in a test tube brown fumes comes out and a black
residue is left behind.
(a) Name the chemical which gives brown fumes.
(b) Write the equation.
(c) Name the compound which gives black residue.​

Answer 1

Answer:

hope it will help u....

Answer 2

Answer:

a) Nitrogen-di-oxide ( $NO_{2}$)

b)2Cu($NO_{3}$)2→2CuO+4$NO_{2}$+ $O_{2}$

c) CuO (black solid)

Explanation:

The chemical that produced such brown fumes is called as Nitrogen-di- Oxide. This is produced because when Copper nitrate is heated, the compound on heating produces brown fumes leading to the formation of  Nitrogen-di-oxide, Copper oxide and Oxygen.

The brown fumes are produced due to the thermal decomposition of nitrates into Nitrogen-di-oxide. Not only for Copper nitrate, nitrates of any compound on undergoing thermal decomposition forms brown fumes and leaves a dark residue behind with respect to the compound with which the nitrate is formed. In case of thermal decomposition of Lead Nitrate, Lead oxide will be formed instead of Copper oxide.

The Copper oxide remains as a residue in the test tube which turns out to be black in color. This reaction is an example of decomposition reaction. A decomposition reaction is a type of reaction where the reactant compounds get decomposed into  fragmented products. Here, it could be clearly seen that Copper nitrate has decomposed into Copper oxide and Nitrogen-di-oxide.

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