Which type of glass is used in the manufacturing of lenses and prisms?

Heating silicon with which of the following at high temperature produces carborundum?

$A$ large amount of energy is released during the formation of $Al_{2}O_{3}$,which is used in which of the following?

How many compounds can be formed when carbon combines with oxygen?

The catenation tendency of $C$,$Si$ and $Ge$ is in the order $Ge < Si < C$. The bond energies (in $kJ \ mol^{-1}$) of $C-C$,$Si-Si$ and $Ge-Ge$ bonds,respectively,are:

Which of the following statements are correct?
$(i)$ $CCl_4$ undergoes hydrolysis easily
$(ii)$ Diamond has directional covalent bonds
$(iii)$ Fullerene is the thermodynamically most stable allotrope of carbon
$(iv)$ Glass is a man-made silicate
The correct answer is