Which of the following aqueous solutions are good buffer systems? . 0.37 M hydrocyanic acid + 0.24 M sodium cyanide 0.14 M sodium nitrite + 0.27 M nitrous acid 0.21 M hypochlorous acid + 0.13 M potassium hypochlorite 0.20 M nitric acid + 0.22 M potassium nitrate 0.32 M ammonium bromide + 0.31 M ammonia

Answer : The good buffer systems are, (a), (b), (c) and (e)

Explanation :

Buffer : It is a solution that prevent any changes in the pH of the solution on the addition of an acidic and basic components.

Or, it is a solution that maintain the pH of the solution by adding the small amount of acid or a base.

There are two types of buffer which are acidic buffer and basic buffer.

Acidic buffer : It is the solution that have the pH less than 7 and it contains weak acid and its salt. For example : Acetic acid (weak acid) and sodium acetate (salt).

Basic buffer : It is the solution that have the pH more than 7 and it contains weak base and its salt. For example : Ammonia (weak base) and ammonium chloride (salt).

The conditions for a good buffer system is:

(1) a weak acid and its conjugate base.

(2) a weak base and its conjugate acid.

(a) 0.37 M hydrocyanic acid + 0.24 M sodium cyanide

It is a combination of weak acid and its conjugate base. So, it is a good buffer.

(b) 0.14 M sodium nitrite + 0.27 M nitrous acid

It is a combination of weak acid and its conjugate base. So, it is a good buffer.

(c) 0.21 M hypochlorous acid + 0.13 M potassium hypochlorite

It is a combination of weak acid and its conjugate base. So, it is a good buffer.

(d) 0.20 M nitric acid + 0.22 M potassium nitrate

It is a combination of strong acid. So, it will not form buffer solution.

(e) 0.32 M ammonium bromide + 0.31 M ammonia

It is a combination of weak base and its conjugate acid. So, it is a good buffer.

Hence, the good buffer systems are, (a), (b), (c) and (e)

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