The coordination number of $Al$ in the crystalline state of $AlCl_3$ is

$SiO_2$ reacts with

How is $H_2S$ liberated in the laboratory?

Which of the following statements is not correct?

The order of catenation power is $Ge < Si < C$. What are the $C-C$,$Si-Si$,and $Ge-Ge$ bond energies (in $kJ/mol$) respectively?

Identify the correct statements from the following.
$(i)$ Quartz is a piezoelectric material.
$(ii)$ All group $14$ tetrachlorides except $CCl_4$ are easily hydrolyzed in water.
$(iii)$ The $C-C$ bond distance within the layer of graphite is $154 \ pm$.
$(iv)$ $SiO_2$ is soluble in aqueous $HCl$ solution.