The pH of a 0.64 M solution of pyridine (C₅H₅N) is 9.52.
A figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline.
The equation for the protonation of the base pyridine is the following:
C₅H₅N + H₂O ⇄ C₅H₅NH⁺ + OH⁻ (1)
Kb = 1.7 × 10⁻⁹ (Given)
To calculate the pH of the solution we need to use the following equation:
pH + pOH = 14
pH = 14 - pOH
=14 - [-log[OH⁻]]
= 14 + log[OH⁻]
Now, we need to find the concentration of the OH⁻ ions. Since pyridine is a weak base, at the equilibrium we have (eq 1):
C₅H₅N + H₂O ⇄ C₅H₅NH⁺ + OH⁻
0.64 - x x x
After entering the values of [C₅H₅N] = 0.64-x, [C₅H₅NH⁺] = x, and [OH⁻] = x, into equation (2) we can find the concentration of OH⁻:
1.7 × 10⁻⁹ =[C₅H₅NH⁺] [OH⁻] / [C₅H₅N]
= x . x / 0.64-x
1.7 × 10⁻⁹ (0.64-x) - x² = 0
Solving the above quadratic equation for x, we have :
Now, We can calculate the pH, after taking the positive value, x₂, (concentrations cannot be negative) and entering into above equation :
pH = 14 + log[OH⁻]
= 14 + log (3.32 x 10⁻⁵)
= 9.52
Therefore, the pH of the solution of pyridine is 9.52.
Find more about pH here:
brainly.com/question/8834103?referrer=searchResults
#SPJ1
