Question

A chemical is heated in a test tube brown fumes comes out and a black residue is left behind name the compound which gives brown fumes

Answer 1

A white salt on heating decomposes to give brown fumes and black residue left
the name of the compound which gives brown fumes is NO2.

Answer 2

A chemical when heated in a test tube gives brown fumes and will leave a black residue that is Nitrogen oxide $(NO_2)$.

Explanation:

• Nitrogen oxide is a 'chemical element' with formula $NO_2$.

• It generate reddish-brown gas at high temperature.

• This reddish-brown gas is due to the absorption of light in the blue

• Also, it is paramagnetic in nature.

• The chemical reaction will be:

      $2Cu(NO_3)_2 \rightarrow 2CuO+ NO_2 +O_2$

• Usually, the nitrogen dioxide will be in brown and when it is evolved, it forms as a gas of brown colour fumes and lead will leave a black colour residue when it is heated.

Learn more about Nitrogen oxide

Properties of paramagnetic ,ferromagnetic and diamagnetic substances

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Why oxygen is paramagnetic in nature by molecular orbital theory

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