$BeO$ reacts with $HF$ in the presence of ammonia to give $[A]$,which on thermal decomposition produces $[B]$ and ammonium fluoride. The oxidation state of $Be$ in $[A]$ is $.....$.

Portland cement is manufactured using which of the following?

Which of the following sulphates is insoluble in water?

$A$ 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:

$Beryllium$ and $magnesium$ do not give colour to flame whereas other alkaline earth metals do so. Why?

Among the following,which is water insoluble?