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Values of dissociation constant , K_{a} are given as follows : 

Acid                                              K_{a}

HCN                                             6.2\times 10^{-10}

HF                                                7.2\times 10^{-4}

HNO_{2}                                       4.0\times 10^{-4}

Correct order of increasing base strength of the base CN^{-},F^{-}\: \: and \: \: NO_{2}^{-}  will be : 

Option: 1


Option: 2


Option: 3


Option: 4


Answers (1)


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.


Posted by

Suraj Bhandari

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