Question

Question 7.40 Classify the following species into Lewis acids and Lewis bases and show how these act as Lewis acid/base:

(a) OH–

(b) F–

(c) H+

(d) BCl3.

Class XI Equilibrium Page 228

Answer 1

concept :-  Lewis acid : Tendency to accept electron.
  according to lewis concept,         
            i) atom having sextet e.g., O, S, Se etc are lewis acid
            ii) electron deficient species e.g., BF₃,BCl₃, AlCl₃ etc are lewis acid.
           iii) molecule in which central atom has one d- orbital e.g., GeX₄,SF₆ etc are lewis acid.
         iv) cation containing a pair of electron less than an inert gas e.g., H⁺, R₃F⁺ etc are lewis acid.
       v) molecule having multiple bonds between two differents electronegatives  atoms. e.g., CO₂,SO₃ etc are lewis acid.

 lewis base : tendency to lose electron.
according to lowis concept,
      i) neutral species having at least one lone pair of electron. e.g., NH₃, ROH, R₂O etc are lewis base.
    ii) simple anion is always lewis base.e.g., H⁻, O⁻⁻, OH⁻⁻  etc are lewis base.

now come to the question,
  from above descriptions you can easily say that,
       (a) (b) are lewis base
and (c) and (d) are lewis acid

Answer 2

Answer:

OH is lewis base

F - is lewis base

H+ is lewis acid

BCl3 is lewis acid

Explanation:

OH is lewis acid because it donate an electron pair

F - is lewis base because it donate an electron pair

H+ is lewis acid because it eccept an electron pair

BCl3 is lewis acid because it accept an electron pair