$17.$ The membrane cell process for caustic soda production uses an ion$-$selective membrane to separate $\_($a$)\_$ and $\_($b$)\_,$ resulting in a pure solution of $\_($c$)\_.$

$-$ a$)$ Chlorine

$-$ b$)$ Hydrogen

$-$ c$)$ Sodium hydroxide

$-$ Options:

$-$ i$)$ Oxygen, Water, Sodium chloride

$-$ ii$)$ Chlorine, Hydrogen, Sodium hydroxide

$-$ iii$)$ Sodium, Chlorine, Water

$18.$ In the Solvay process, $\_($a$)\_$ is recovered by reacting $\_($b$)\_$ with $\_($c$)\_$ to form calcium chloride and ammonia.

$-$ a$)$ Ammonia

$-$ b$)$ Ammonium chloride

$-$ c$)$ Calcium hydroxide

$-$ Options:

$-$ i$)$ Carbon dioxide, Calcium carbonate, Sodium bicarbonate

$-$ ii$)$ Ammonia, Ammonium chloride, Calcium hydroxide

$-$ iii$)$ Calcium chloride, Sodium chloride, Water