Which of the following sulphates is insoluble in water?

Which of the following is the correct order of basic strength?

Which among the following elements of group-$2$ exhibits anomalous properties?

Gypsum $CaSO_4 \cdot 2H_2O$ on heating to about $120\ ^\circ C$ forms a compound which has the chemical composition represented by :-

Which of the following compounds is used for the preparation of quicklime?

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