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)

here we have to get the change of moles on decrease the volume of the reaction in gas phase.

the   per the given options it will decrease by (d) 11-50%

we know, on decreasing the volume of the gas phase reaction the reaction moves to the product side.

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:                   1 - α               α               α           = 1 + α

(concentration = moles/volume, as volume is 1 l)

(where α is the degree of dissociation)

now the dissociation constant in terms of concentration is :

=  

or,

or,   = (at v = 1l)

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:               (1 - α)/0.5           α/0.5         α/0.5       = (1 + α)/0.5

thus, the dissociation constant in terms of concentration is :

or,  

=  

so, the change of 1 : 1/0.5

or, 1: 2

thus it will decrease by 50%.

or, as per the given options it will decrease by 11-50%

a

explanation: