Question

The acid-dissociation constant, ka, for gallic acid is 4.57 ⋅ 10-3. what is the base-dissociation constant, kb, for the gallate ion? the acid-dissociation constant, ka, for gallic acid is 4.57 10-3. what is the base-dissociation constant, kb, for the gallate ion? 2.19 ⋅ 10-12 2.19 ⋅ 102 5.43 ⋅ 10-5 4.57 ⋅ 10-3 7.81 ⋅ 10-6

Answer 1

Answer: The base dissociation constant for a conjugate base is $2.18\times 10^{-12}$

Explanation:

To calculate the base dissociation constant for the given acid dissociation constant, we use the equation:

$K_w=K_b\times K_a$

where,

$K_w$ = Ionic product of water = $10^{-14}$

$K_a$ = Acid dissociation constant = $4.57\times 10^{-3}$

$K_b$ Base dissociation constant = ?

Putting values in above equation, we get:

$10^{-14}=4.57\times 10^{-3}\times K_b\\\\K_b=2.18\times 10^{-12}$

Hence, the base dissociation constant for a conjugate base is $2.18\times 10^{-12}$

Answer 2

Hello!

To determine the Kb of gallic acid is actually very simple. 

The dissociation reaction of Gallic Acid (HGal) is the following:

HGal+H₂O ⇄ H₃O⁺ + Gal⁻

The equation for converting from Ka to Kb is the following:

$Ka*Kb=Kw \\ \\ Kb= \frac{Kw}{Ka}= \frac{1*10^{-14} }{4,57*10^{-3} }=2,19 * 10^{-12}$

So, the Kb is 2,19*10⁻¹²

Have a nice day!