Terminal alkynes `(RC-=CH)` are not reduced by alkali metals (e.g., Na, K, or Li) in liq. `NH_3`, but reduction takes place when `(NH_4)_2SO_4` is added in the reaction mixture. Explain why.

CaSO_(4) is insoluble but is not precipitated when excess of (NH_(4))_(2)SO_(4) is added to CaCl_(2) . Explain

In the conversion of alkyne to trans -alkene by birch reduction using alkali metals (such as Na or K) in liquid NH_3 and alcohol (MeOH or EtOH), The mechanism takes place in the formation of intermediate species in the following sequence:

When K_(2)MnO_(4) is added in solution of NH_(4)Cl then

When K_(2)MnO_(4) is added in solution of NH_(4)Cl then