Question

Question: Identify which of the following combination will be able to constitute a buffer.
Problem 1		Problem 2				Problem 3
HCN (aq) + HSCN (aq)	yes; no.	HNO3 (aq) + NO3- (aq)		yes; no.		HClO3 (aq) + ClO3- (aq)	yes; no.
HC2H3O (aq) + C2H3O- (aq)	yes; no.	HNO2 (aq) +NaNO2(aq)		yes; no.		HClO (aq) + KClO (aq)	yes; no.
Cl- (aq) + HCl (aq)	yes; no.	NH4+(aq) + NH3 (aq)		yes; no.		NaH2PO4 (aq) + Na2HPO4 (aq)	yes; no.
H2S (aq) + Na2S (aq)	yes; no.	H2SO4 (aq) +Na2SO4(aq)		yes; no.		H2CO3 (aq) +NaHCO3(aq)	yes; no.

Answer 1

Buffer is a solution of weak acid and its conjugate base or weak base and its conjugate acid.

Therefore the following combination are able to consititute a buffer.

HC₂H₃O (aq) + C₂H₃O^- (aq)

H₂S(aq) + Na₂S (aq)

HNO_{2 (aq)}  + NaNO_{2 (aq)}

NH₄⁺ (aq) + NH₃ (aq)

HClO (aq) + KClO (aq)

NaH₂PO₄ (aq) + Na₂HPO₄ (aq)

H₂CO₃ (aq) + NaHCO₃ (aq) .

HCl, HNO₃, H₂SO₄ and HClO₃ are strong acid they can not form buffer . HCN and HSCN are both weak acids hence their combination can not act as buffer.