Identify Lewis acids and Lewis bases in the following reactions and give reactions: (1) `SiF_(4)+2F^(-)toSiF_(6)^(2-)`
(2) `RMgX+2(C_(2)H_(5))_(2)overset(..)(O): to RM g[O(C_(2)H_(5))_(2)]_(2)X`
(3) `Ag^(+)+2overset(..)(N)H_(3) to [Ag(NH_(3))_(2)]^(+)`
(4) `overset(..)(N)H_(3)+H^(+)to overset(+)(N)H_(4)`.

Explanation

According to Lewis concept, an acid is a substance which can accept one or more electron pari(s). Generally, cations (such as `Ag^(+),H^(+),K^(+)`), compounds having a central atom with incomplete octet (such as `SiF_(4),AlF_(4),RMgX,BF_(3)`) and compounds whose central atom is linked to an electronegative atom by double bond (such as `CO_(2)`) can act as lewis acid. in the given reactions, Lewis acids are: `SiF_(6),RMgX,Ag^(+),H^(+)`. According to lewis concept, a base is a substance which can donate one or more electron pair(s). anions (such as `F^(-),OH^(-)`) and compounds with lone pair of electrons cann act as lewis base. Therefore, in the given reactions, Lewis bases are: `F^(-),NH_(3),(C_(2)H_(5))_(2)O and NH_(3)`.