Among the alkaline earth metals,the element forming predominantly covalent compounds is:

$A$ compound $x$ on heating gives a colourless gas. The residue is dissolved in water to obtain $y$. Excess $CO_2$ is bubbled through the aqueous solution of $y$ and $z$ is formed. $z$ on gentle heating gives back $x$. The compound $x$ is:

Why is cement known as Portland cement?

Select the correct statement from the following.

Bleaching powder is correctly represented as

Which of the following substances is insoluble in water?