Question

Take copper nitrate in a test tube and heat it over the flame.
i.) What is the colour of cupric nitrate?
ii.) What do you observe?
iii.) Name the type of reaction that takes place.
iv.) Write the balanced equation.

Answer 1

Hint: The colour of cupric nitrate is the same as that of hydrated copper sulphate. We observe the breaking of copper nitrate into two gases and a solid product on heating. One gas is coloured while the other one is not seen with naked eyes.

Complete answer :
First, let's use what is copper nitrate and what happens on heating.
So, the copper nitrate is an inorganic compound used for nitration of aromatic compounds in combination with acetic anhydride. It has a chemical formula of $Cu{(N{O_3})_2}$. It is a blue crystalline solid in nature.
When copper nitrate is heated in the test tube, it decomposes into copper oxide, nitrogen dioxide and oxygen gas. Initially, a molecule of water is lost and on further heating, we get nitrogen dioxide and oxygen gas.
Now, let us see the questions.
The first one is what is the colour of cupric nitrate.
So, the colour of copper nitrate is blue.
The second question is what do you observe.
By observation, we mean the things visible to us and we can see only the coloured things. So, we observe reddish-brown fumes of nitrogen dioxide that are emitted.
The third is that name is the type of reaction that takes place.
It is a decomposition reaction in which the reactant breaks into various products on absorption of energy in the form of heat.
The last one is to write the balanced equation for the reaction.
The chemical equation is -
$2Cu{(N{O_3})_2}\xrightarrow{{heat}}2CuO + 4N{O_2} \uparrow + {O_2} \uparrow $
The two gases evolve as the reactant decomposes.

Note :
During the observation, we say that we see reddish brown fumes of nitrogen dioxide but we do not say about oxygen. This is because oxygen is transparent and thus is not visible to us. So, the oxygen can not be the answer.
Further, the copper(II) nitrate and the cupric nitrate are one and the same thing. So, the examiner is asking about the initial colour of the reactant.