The commercial name for calcium oxide is

Fill in the blanks:
$(1)$ Calcium and beryllium have flame colors of ...... and ....... respectively.
$(2)$ Quantitative analysis of calcium is carried out by ........
$(3)$ Beryllium powder on combustion burns brightly in air and gives ...... and .......
$(4)$ Beryllium hydroxide on dissolving in alkali gives .......

Give the uses of cement.

What is the difference in the number of water molecules between gypsum and plaster of Paris?

Bleaching powder is obtained by the reaction of chlorine gas with ........

$X + C + Cl_2 \xrightarrow[> 1000 \ K]{\text{High temp.}} Y + CO$
$Y + 2H_2O \to Z + 2HCl$
Compound $Y$ is found in a polymeric chain structure and is an electron-deficient molecule. $Y$ must be: