Question

Which of the following aqueous solutions are good buffer systems? 

• 0.33 M nitrous acid + 0.27 M potassium nitrite 

• 0.24 M nitric acid + 0.23 M sodium nitrate 

• 0.32 M ammonium nitrate + 0.33 M ammonia 

• 0.16 M hypochlorous acid + 0.12 M sodium hypochlorite 

• 0.16 M potassium fluoride + 0.28 M hydrofluoric acid

Answer 1

Acidic buffer solution is formed by mixing a weak acid and its salt of strong base i.e. its conjugate base.

Basic buffer solution is formed by mixing a weak base and its salt of strong acid i.e. its conjugate acid.

Therefore,

The good buffer solutions are :

(a). 0.33 M nitrous acid + 0.27 M potassium nitrite, Because, HNO₂ is a weak acid and potassium fluoride i.e. NO₂^- is its conjugate base which form a acidic buffer solution.

(b). 0.32 M ammonium nitrate + 0.33 M NH₃ , Because, NH₃ is a weak base and ammonium nitrate i.e. NH₄⁺ is its conjugate base which form a basic buffer solution.

(c). 0.16 M hypochlorous + 0.12 M sodium hypochlorite, Because, HClO is a weak acid and sodium hypochlorite i.e. ClO^- is its conjugate base which form a acidic buffer solution.

(d). 0.16 M potassium fluoride + 0.28 M hydrofluoric acid, Because, HF is a weak acid and potassium fluoride i.e. F^- is its conjugate base which form a acidic buffer solution.

On the other hand, HNO₃ is the strong acidic therefore not form a buffer solution.