Question

Which is the strongest bronsted base cn-,cl-,i-,br-?

Answer 1

Answer:

CN-

Explanation:

It's conjugate acid HCN is the weakest, hence it's base which is CN- will be the strongest.

Answer 2

Answer:

Among the given options, the CN⁻ is the strongest Bronsted base.

Therefore, the option (1) is correct.

Explanation:

• According to the Bronsted-Lowry concept, a base is the substance which can accept the proton. The base which is formed from the acid is called conjugate base of the acid.

• The strength of base depends upon the tendency to accept the proton. Conjugate base of strong acid is a weak base.

• The acidic strength of hydroacids of halogen as : HI> HBr > HCl > HF. Strength of their conjugate base will be I⁻ < Br⁻ < Cl⁻ < F⁻

• Now if we compare the HCN and HCl, then HCN is a very weak acid in the comparison of HCl. The pka value of HCl is -5.9 while for HCN pka value is 9.2. In hydrogen cyanide, hydrogen is covalently  bonded to sp hybridized carbon which is reluctant to donate H⁺ ion.

        HCN    ⇄      H⁺     +       CN⁻

        acid                             conjugate base    

• HCN is a weakest acid, therefore its conjugate base will be the strongest base.