Respuesta :

PBCHEM
Answer : The acid strength of HCl is strongest among the given series.
So, the strength decreases as per this trend HCl > [tex] HSO_{4} ^{-} [/tex] > HCN;

So when identifying the weakest base it has to be CN as it has less acid strength as compared to the series as it acts as a lewis base which donates its pair of electrons. They are weak bases generally but when compared with acids they are considered to be the strongest. 
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