A 1.0 m solution of a compound with 2 ionizable groups (pka's = 6.2 and 9.5; 100 ml total) has a ph of 6.8. what are the concentrations of the relevant acid and conjugate base?

[H₂A] = 0.2M

[HA⁻] = 0.8M

Explanation:

A compound with 2 ionizable groups has as equilbriums:

H₂A ⇄ HA⁻ + H⁺ ⇄ A²⁻ + H⁺

A pH of 6.8 is near to the first equilibrium:

H₂A ⇄ HA⁻ + H pKa = 6.2

To determine concentrations of the acid H₂A and conjugate base HA⁻ we use H-H equation:

pH = pKA + log [HA⁻] / [H₂A]

6.8 = 6.2 + log [HA⁻] / [H₂A]

0.6 = log [HA⁻] / [H₂A]

3.981 = [HA⁻] / [H₂A] (1)

As concentration of the buffer is 1.0M:

1M = [HA⁻] + [H₂A] (2)

Replacing (2) in (1):

3.981 = 1- [H₂A] / [H₂A]

3.981[H₂A] = 1 - [H₂A]

4.981 [H₂A] = 1

[H₂A] = 0.2M

And [HA] = 1M - 0.2M = 0.8M

answer: e.   sour taste

explanation: acids are those substances which dissociates in water to give ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. acids are sour in taste. example: hcl

bases are those substances which dissociates in water to give ions or accepts ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. bases are bitter in taste. bases are slippery in nature.