Why liquid `NH_(3)` can be used as refrigerating agent?

Explain why liquid ammonia is used as a refrigerant.

Liquid ammonia is widely used as a refrigerant-why?

Why does NH_(3) act as a Lewis base?

…………………… is used as a foaming agent.

Why alkali metals are used as reducing agents?

Neither vinyl chloride (CH_2=CH-Cl) nor chlorobenzene (C_6H_5-Cl) can be used as alkylating agent in the Friedel-Crafts reaction -Why ?

Explain why the Sn (II) salts are used as reducing agents while Pb (IV) salts are used as oxidising agents.