Values of dissociation constant , are given as follows :
Acid
HCN
HF
Correct order of increasing base strength of the base will be :
As we know that,
Higher the value of Ka lower is the value of PKa i.e. higher will be the acidic nature. Further since CN-, F- and NO2- are conjugate base of the acids HCN, HF, HNO2 respectively. Hence, the correct order of base strength will be F-< NO2-< CN-
Since, stronger the acids weaker will be it's conjugate base.
Hence, the option number (3) is correct.
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