We are given the base dissociation constant, Kb, for Pyridine (C5H5N) which is 1.4x10^-9. The acid dissociation constant, Ka for the Pyridium ion or the conjugate acid of Pyridine is to be determined. We know from our chemistry classes that:
Kw = Kb * Ka
where Kw is always equal to 1x10^-14
so, to solve for Ka of Pyridium ion, substitute Kb to the equation together with Kw and solve for Ka:
1x10^-14 = 1.4x10^-9 * Ka
solve for Ka
Ka = 7.14x10^-6
Therefore, the acid dissociation constant of Pyridinium ion is 7.14x10^-6.
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I think it's easiest to find the pOH from the given [OH-] first.
-log(1x10^-5)
pOH=5
Then find the pH.
pOH+pH=14
5+pH=14
pH=9
Then find the [H+] using the pH.
antilog(-9) (if you dont have an antilog button use 10^-9)
[H+]=1x10^-9
The density of the wood : 1.45 g/cm³
<h3>Further explanation </h3>
Density is a quantity derived from the mass and volume
Density is the ratio of mass per unit volume
With the same mass, the volume of objects that have a high density will be smaller than objects with a smaller type of density
The unit of density can be expressed in g/cm³ or kg/m³
Density formula:

ρ = density
m = mass
v = volume

