Question

Which of the following aqueous solutions are good buffer systems? . 0.36 M sodium perchlorate + 0.28 M sodium chloride 0.11 M hypochlorous acid + 0.13 M sodium hypochlorite 0.29 M hydrobromic acid + 0.19 M potassium bromide 0.34 M ammonia + 0.32 M ammonium bromide 0.15 M potassium hydroxide + 0.25 M potassium bromide

Answer 1

Buffer solutions -->

A buffer is any type of substance that will resist pH change when H+ or OH- is added.

This is typically achieved with equilibrium equations. Both type of buffer will resist both type of additions.

When a weak acid and its conjugate base are added, they will form a buffer

The equations:

The Weak acid equilibrium:

HA(aq) <-> H+(aq) + A-(aq)

Weak acid = HA(aq)

Conjugate base = A-(aq)

Neutralization of H+ ions:

A-(aq) + H+(aq) <-> HA(aq); in this case, HA is formed, H+ is neutralized as well as A-, the conjugate

Neutralization of OH- ions:

HA(aq) + OH-(aq) <-> H2O(l) + A-(aq) ; in this case; A- is formed, OH- is neutralized as well as HA.

Now,

For the weak base equilibrium:

B(aq) + H2O(l) <-> BH+(aq) + OH-(aq)

Weak base = B;

Conjugate acid = BH+

Neutralization of OH- ions:

BH+(aq) + OH-(aq) <-> B(aq) + H2O(l); in this case, OH- is neutralized by BH+, as well as B is created

Neutralization of H+ ions:

B(aq) + H+(aq) <-> BH+(aq)

A) 0.36 M sodium perchlorate + 0.28 M sodium chloride

no acid/base present

B) 0.11 M hypochlorous acid + 0.13 M sodium hypochlorite

HClO + NaOCl --> this will form acidic buffer

C) 0.29 M hydrobromic acid + 0.19 M potassium bromide

strong acid --> will not form buffer

d) 0.34 M ammonia + 0.32 M ammonium bromide

this forms a bsic buffer, NH3 and NH4+

e) 0.15 M potassium hydroxide + 0.25 M potassium bromide

storng base wil not form a buffer