Which of the following solutions cannot act as buffer system ?

Options

A. `KH_(2)PO_(4)//H_(3)PO_(4)`
B. `NaCIO_(4)//HCIO_(4)`
C. `C_(5)H_(5)N//C_(5)H_(5)NHHCI`
D. `Na_(2)CO_(3)//NaHCO_(3)`

Answer

B

Explanation

A buffer solution is a solution of (i) a weak acid or base and (ii) its salt, both components must be present.
(1) `H_(3)PO_(4)` is a weak acid, and its conjugate base, `H_(2)PO_(4)^(-)`, is a weak base. Therefore, this is a buffer system.
(2) Because `HCIO_(4)` is a strong acid, its conjugate base, `CIO_(4)^(-)`, is an extremely weak base. This means that the `CIO_(4)^(-)` will not combine with an `H^(+)` ion in solution to form `HCIO_(4)`. Thus, the system cannot act as a buffer system.
(3) `C_(5)H_(5)N` (pyridine) is a weak base and its conjugate acid, `C_(5)H_(5)N^(+)H` (the cation of the salt `C_(5)H_(5)NHHCI)`, is a weak acid. Thus this a buffer system.
(4) `HCO_(3)^(-)` (anion of the salt `NaHCO_(3)`) is a weak acid, and its conjugate base, `CO_(3)^(2-)` (anion of the salt `Na_(2)CO_(3))`, is a weak base. Therefore, this is a buffer system.