Which of the following acids is formed when $SiF_4$ reacts with water?

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{P}OCl_3 + H_2O \longrightarrow H_3PO_4 + HCl$

$PbI_4$ does not exist because

What is the product formed in the reaction $SnO_2 + HCl$ (excess)?

Give a brief account of the production of cement and write its properties and uses.

In which one of the following pairs,both oxides are acidic?