Question

Choose the correct option.
Assertion: Carbon dioxide is gas but silicon dioxide is an in-fusible solid.
Reason: Carbon dioxide has a linear ${\rm{\pi }}$- bonded structure.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. The assertion is correct but the Reason is incorrect
D. Both Assertion and Reason are incorrect.

Answer 1

Carbon and silicon both belong to the same group of the periodic table i.e. group 14 and carbon is the first element in this group, hence it is also called the carbon family. Carbon is the first element and also shows some anomalous behavior from the rest of the group.

Complete answer:
Let’s see whether or not these statements are correct or not. We know that carbon dioxide (${\rm{C}}{{\rm{O}}_2}$) is a gas that is present in the environment but why is it a gas?
Carbon dioxide is formed by only 3 atoms (i.e., 2 oxygen and 1 carbon) small molecule, the bonds are formed by weak intermolecular attraction and has a linear ${\rm{\pi }}$- bonded structure ($O=C=O$), therefore, it is found as a gas in normal temperature.
While in the case of silicon dioxide (${\rm{Si}}{{\rm{O}}_2}$), the silicon-oxygen bond is unstable as a result silicon dioxide molecule is present in a vast 3-dimensions structure, where every silicon is bonded with 4 oxygen, and one oxygen is bonded with 2 silicon, this vast structure of 3-dimension network ${\rm{Si}}{{\rm{O}}_2}$ forms a crystal and this solid ${\rm{Si}}{{\rm{O}}_2}$ is very stable that’s why ${\rm{Si}}{{\rm{O}}_2}$ has high boiling point.
Therefore, we can conclude that both assertion and reason are correct, but the reason is not the correct explanation for the assertion.

**Hence, the correct answer is option (B) i.e., Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Note:**
One may get confused with option (C) (i.e., The assertion is correct but the Reason is incorrect) because the reason is correct as an independent statement but not if we consider it to be the reason for the carbon dioxide being a gas. ${\rm{C}}{{\rm{O}}_2}$ is a gas at room temperature because of its weak intermolecular attraction.