Question

What is the colour of the product formed when copper carbonate decomposes ?
A. Blue
B. Black
C. Yellow
D. White

Answer 1

Hint:Few compounds get broken down on heating and form two or more than two products from the reactant. This process of decomposition by heating is called thermal decomposition. The color of the products formed during the thermal decomposition is different from the color of the reactants due to heat.

Complete step-by-step answer:- In the question it is given that copper carbonate decomposes to copper oxide and carbon dioxide.
- We have to find the color of the residue formed during the decomposition.
- The molecular formula of copper carbonate is $CuC{{O}_{3}}$ .
- The molecular formula of copper oxide is CuO.
- The molecular formula of carbon dioxide is $C{{O}_{2}}$ .
- The decomposition of the copper carbonate is as follows.
$CuC{{O}_{3}}\xrightarrow{decomposition}CuO+C{{O}_{2}}$
- Generally the color of the copper carbonate is green.
- After heating it produces copper oxide residue and carbon dioxide gas as the products.
- After thermal decomposition the color of the copper oxide residue is black.
- Therefore the color of the residue after decomposition of copper carbonate is black.
-
So, the correct option is B.

Note:The carbon dioxide produced in the decomposition of copper carbonate can be tested by using lime water. The lime water is going to convert to milky when carbon dioxide reacts with it. The reaction of carbon dioxide with lime water is as follows.
\[C{{O}_{2}}+\underset{\lim e\text{ }water}{\mathop{Ca{{(OH)}_{2}}}}\,\to \underset{milky\text{ }white}{\mathop{CaC{{O}_{3}}}}\,+{{H}_{2}}O\]
The milky white color is due to the formation of calcium carbonate.