Question

Each of the following mixtures can produce an effective buffer solution?

1]1.00 MNaClO2 and 0.0100 M HClO2

2]>0.025 M CH3NH3 and 0.030 M CH3NH3Cl

3] 0.10 M NH3 and 0.10 M HC2H3O2

Answer 1

First, let us define a buffer:

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)

then

from our data:

Q1.

NaClO2 + HClO2

it has HClO2, weak acid + ClO2- conjguate base, this is a good buffer!

Q2.

special note: CH3NH3 is not likely to exist, this is either CH3NH2 OR CH3NH3+;

if this is CH3NH2; then this is a good fit since there is a conjguate acid in CH3NH3Cl

if this is CH3NH3+; this is not a good fit, since there is only presence of conjguate acid, CH3NH3+ and no base

Q3.

weak base + weak acid = in equal conditions, they will be a buffer

since the conjugate will form if H+ is added:

NH3 + H = NH4+ and CH3COOH

and the conjugate will form when OH- is added

CH3COOH + Oh- = CH3COO- + H2O

this forms a buffer