$BaSO_4$ and carbon on heating react to produce:

An alkaline earth metal $(M)$ gives a salt with chlorine,which is insoluble in water at room temperature but soluble in boiling water. It also forms an insoluble sulphate whose mixture with a sulphide of a transition metal is called 'lithopone' - a white pigment. Metal $M$ is

The compound $A$ on heating gives a colourless gas and a residue that is dissolved in water to obtain $B$. Excess of $CO_2$ is bubbled through aqueous solution of $B$,$C$ is formed which is recovered in the solid form. Solid $C$ on gentle heating gives back $A$. The compound $A$ is:

In the alkaline earth metals,the element forming predominantly covalent compounds is

The white enamel of our teeth is composed of:

$A$ mixture of $MgCl_2$ and $MgO$ is called