Which compound is used in medicine as a barium meal for intestinal $X$-ray?

Which of the following alkaline-earth metal hydroxides is the strongest base?

$Ba$,$Ca$,and $Sr$ form halide hydrates. Their formulas are $BaCl_2 \cdot x H_2 O$,$CaCl_2 \cdot y H_2 O$,and $SrCl_2 \cdot z H_2 O$. The values of $x$,$y$,and $z$ respectively are:

Alkaline earth metals (except $Be$) can easily lose their valence electrons,so how do they behave?

Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?

Which of the following compounds is obtained when carbon dioxide gas is bubbled through a slaked lime solution?