1st and 3rd reaction:
Dissolving those compunds in water you get a mixture of anions and cations: the only reaction possible is the precipitation of an "insoluble" salt. Checking the Ksp values you'll see that:
(CaSO4) Ksp=2.4∙10-5
(BaSO4) Ksp=1.1∙10-10
2nd reaction:
It's simply the oxidation of an alkali metal due to oxygen. What is the only oxidation state of alkali metals?