Answer the following:
(a) Why is `BBr_(3)` a stronger Lewis acid as compared to `BF_(3)` thoughF is more electronegative than Br?
(b) Why is `(CH_(3))_(2)` COH is less acidic than `(CH_(3))_(3)` SiOH although C is more electronegative than Si?

Explanation

(a) This is explained with the help of concept of back b onding since F is in a positon to cause greater back bonding (2p orbtials of both B and F participitate) than Br (4p orbitals of Br and 2p orbtial of B participate), tehrefore `BBr_(3)` is a stronger Lewis acid than `BF_(3)`
(b) In `(CH_(3))_(2)SiOH`, the central silicon atom has vacant d-orbitals which can acc ept electron paris from Lewis base However, the carbon atom in `(CH_(3))_(2)COH` is not in a postion to doe so since it has no vacant d-orbitals. Therefore `(CH_(3))_(3)SiOH` is more acidic (Lewis acid) than `(CH_(3))(3)COH`.