Which pair of compounds will form a buffer in aqueous solution? a) HCN and NaCN b) HCl and NaOH c) NaCN and NaOH d) HCN and HCl e) HCl and NaCl f) NaCN and KCN

a) HCN and NaCN

Explanation:

Buffer solution is made by mixing either a weak base and its salt like ammonia and ammonium chloride or weak acid and its salt like HCN and its salt NaCN or acetic acid and sodium acetate .

In the given option , all of the rest of option has either strong acid or strong base or both  . In the last option both are salt so it can not form buffer solution .

It is capable of keeping the pH of the solution constant .