Question

Which involves breaking of covalent bonds?

• A. Boiling of $H_{2}S$
• B. Melting of $Si{O}_2$
• C. Melting of $KCN$
• D. Boiling of $CC{l}_4$

Answer 1

The correct option is B Melting of $Si{O}_2$

Silica has a three-dimensional network structure. In silica, silicon is $s{p}^3$ - hybridized and is thus linked to four oxygen atoms and each oxygen atom is linked to two silicon atoms forming a three-dimensional giant molecule as shown in figure. This three-dimensional network structure imparts stability to $Si{O}_2$ crystal and hence a large amount of energy is required to break the crystal resulting in high melting point.
And melting of this breaks covalent bonds between molecules.