Answer :
Final answer:
The concentration of hydroxide ions ([OH-]) in a 0.255 M solution of pyridine is calculated to be 2.07 x 10^-5 M using the base dissociation constant (Kb) and the assumption of x representing the concentration of [OH-] and [C5H5NH+].
Explanation:
To calculate the concentration of hydroxide ions ([OH) for a solution of pyridine (C5H5N), we can use the base dissociation constant (Kb). The Kb expression for pyridine in water is given by: Kb = [C5H5NH+][OH-] / [C5H5N].
We assume that the concentration of [C5H5NH+] and [OH-] are both equal to 'x' because pyridine is a weak base and only partially ionizes in solution. Thus, the Kb equation can be rewritten as: Kb = (x)(x) / (0.255 - x), where we neglect 'x' in the denominator due to its small value compared to 0.255 M.
Solving for 'x' yields: x2 / 0.255 = 1.69 x 10-9, and x = sqrt((1.69 x 10-9) * 0.255) = 2.07 x 10-5 M. Therefore, [OH-] = 2.07 x 10-5 M.
