Kb for aniline is 4.3 x 10^-10. What does this tell you about aniline? Please help!
It tells you it is a weak base.
If we call aniline phNH2 (ph is for C6H5), then in water solution,
phNH2 + HOH ==> phNH3^+ + OH^-
Kb = (phNH3^+)(OH^-)/(phNH2)
Write the Kb and this equation on paper. Kb = 4.3 x 10^-10.
Note that for that fraction to be less than 1 (and 4.3 x 10^-10 is WAY less than 1), the products (in the numerator) MUST be MUCH smaller than the reactants (in the denominator) so it means that there is very little phNH3^+ and very little OH^- and that most of the material is in the form of aniline. That means that the reaction occurred to a very small extent.
Well, 4.3 x 10^-10 seems like a pretty small Kb value, doesn't it? It's so small, it's almost Kb-surd! Okay, okay, enough with the wordplay. Now, let's get serious.
The Kb value in this case stands for the base dissociation constant for the compound aniline. Aniline is a weak base, so a low Kb value tells us that it doesn't readily dissociate in water and doesn't produce many hydroxide ions (OH-). In other words, aniline is not very good at playing the base role in a solution.
So, if you were expecting aniline to be super-basic, you might be disappointed. But hey, look at the bright side - aniline is still an interesting compound with its own unique qualities. Keep your chemistry curiosity alive, my friend!
The K_b value for aniline, which is 4.3 x 10^-10, provides information about its basicity. K_b is the equilibrium constant for the reaction of a base with water to form the conjugate acid and hydroxide ion.
A lower value of K_b indicates a weaker base, while a higher value indicates a stronger base. Since the K_b value for aniline is very small, 4.3 x 10^-10, it suggests that aniline is a weak base.
The value you mentioned, 4.3 x 10^-10, represents the dissociation constant (Kb) of aniline. Kb is a measure of how well a base (in this case, aniline) dissociates in water to form hydroxide ions (OH^-).
Aniline is a weak base, meaning it does partially dissociate in water, but not completely. The Kb value tells you the extent to which aniline dissociates in water. In this case, the smaller the Kb value, the weaker the base.
To calculate the concentration of hydroxide ions produced from aniline in water, you would need to set up an equilibrium expression using the Kb value:
Kb = [OH^-][C6H5NH+]/[C6H5NH]
Where [OH^-] is the concentration of hydroxide ions, [C6H5NH+] is the concentration of the dissociated form of aniline (aniline with one less hydrogen ion, known as the conjugate acid), and [C6H5NH] is the concentration of the original undissociated aniline.
By solving this equation, you can determine the concentration of hydroxide ions produced when aniline is dissolved in water, which will help you understand the basicity of aniline.