Question

Graphite is a good conductor of heat and electricity because it contains:
A. layers of carbon atoms.
B. sheet like structure.
C. free electrons.
D. $p\pi - p\pi $ bonding.

Answer 1

Hint: For solving this question, we need to focus on the structure of Graphite. -Graphite has a two dimensional sheet like structure and its sheet can be considered as a fused system of planar hexagonal rings.
-When we talk about planar hexagonal rings, we know that each carbon atom is bonded to three other carbon atoms.
-We have to know that the colour of graphite is greyish black and is an opaque substance. Graphite is made up of carbon. A huge amount of pressure has to be applied to break the covalent bonds in graphite.

Complete step by step answer:
We know that Graphite contains carbon atoms which have strong covalent bonds in each layer that shows $s{p^2}$ hybridization and weaker forces that hold the layers together. Hence, that makes it a good conductor of heat and electricity. It is very soft and slippery and for this reason, graphite can be used as lubricant in machines running at high temperature, where oil cannot be used as lubricant. The sheet-like structure gives graphite a soft material.

From the structure of graphite, we know that $\pi $-electrons are free to move throughout the entire layers so graphite is a good conductor of electricity. Its conductivity increases with temperature because of these free electrons it is a heat conductor.
Therefore, the option C is correct.

Note:
We also know that covalent solids are made up of atoms connected by covalent bonds. They can be characterized as being very hard with very high melting points which make them poor conductors of heat and electricity as there are no free charges. Also, covalent solids are incapable of dissolving. For example we can consider the structure of diamonds and graphite, etc.