1.

Values of dissociation constant,K_(a) are given as follows : Acid K_(a) HCN 6.2xx10^(-10) HF "" 6.6xx10^(-4) HNO_(2) "" 7.2xx10^(-4) Correct order of increasing base strength of the base CN^(-), F^(-) and NO_(2)^(-) will be :

Answer»

`F^(-) lt CN^(-) lt NO_(2)^(-)`
`NO_(2)^(-) lt CN^(-) lt F^(-)`
`F^(-) lt NO_(2)^(-) lt CN^(-)`
`NO_(2)^(-) lt F^(-) lt CN^(-)`

Solution :Higher the value of `K_(a)` lower will be the value of `pK_(a)` IE., higher will be the acidic nature. Further since `CN^(-),F^(-) and NO_(2)^(-)` are conjugate BASE of the acids HCN, HF and `HNO_(2)` respectively hence the correct order of base strength will be
`F^(-) lt NO_(2)^(-) lt CN^(-)`
`(because` stronger the ACID weaker will be its conjugate base)


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