Which pair of atomic numbers represents $s$-block elements?

Mercury is transported in containers made of

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ Lithium salts are hydrated.
Reason $(R):$ Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements,choose the most appropriate answer from the options given below:

Sodium is produced by the electrolysis of a molten mixture of about $40\%$ $NaCl$ and $60\%$ $CaCl_2$ because

Which pair of metals dissolves in $NaOH$ solution?

Sodium carbonate is manufactured by the Solvay process. The products that are recycled are: