Which of the following properties of alkaline earth metals increases with an increase in their atomic number?

Which of the following metal carbonates decomposes on heating?

The oxide,which is best soluble in $H_2O$ is

Choose the correct statements from the following:
$(I)$ In vapour phase $BeCl_2$ exists as a chlorobridged dimer.
$(II)$ $BeSO_4$ is readily soluble in water.
$(III)$ $BeO$ is completely basic in nature.
$(IV)$ $BeCO_3$ being unstable, is kept in an atmosphere of $CO_2$.
$(V)$ $BeCO_3$ is the least soluble among all the carbonates of group $2$ elements.

The setting of Plaster of Paris is:

Bleaching powder is obtained by passing chlorine on