Which chloride does not exist as hydrate?

Which of the following salts does not produce nitrogen dioxide $(NO_2)$ upon heating?

The strongest reducing agent among the following is:

State as to why:
$(a)$ a solution of $Na_2CO_3$ is alkaline?
$(b)$ alkali metals are prepared by electrolysis of their fused chlorides?
$(c)$ sodium is found to be more useful than potassium?

Solvay's process is used for the preparation of

Which compound has the lowest thermal stability?