Choose the acidic oxide from the following.

In the following reaction,assign the correct category for the underlined atom based on the product of complete hydrolysis at $R.T.$:
$\underline{Si}F_4 + 2H_2O \longrightarrow H_4SiO_4 + 4HF$

Correct statements among $(i)$ to $(iv)$ regarding silicones are:
$(i)$ they are polymers with hydrophobic character
$(ii)$ they are biocompatible
$(iii)$ in general,they have high thermal stability and low dielectric strength
$(iv)$ usually they are resistant to oxidation and used as greases.

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

Which of the following is the correct statement for red lead?

$SiO_2$ reacts with