Calculate the pH of a solution of 1.5 × 10-5 M NH4OH. What is the result?

To determine the pH of a solution of ammonium hydroxide (NH4OH), which is a weak base, we first need to recognize that it partially dissociates in water to form NH4+ and OH-. The concentration of OH- produced through this dissociation can be calculated using the base dissociation constant (Kb) of NH4OH.

Given that ammonium hydroxide is a weak base, we can use the Kb value for NH4OH (around 1.8 × 10^-5) to set up a dissociation equilibrium expression:

[ K_b = \frac{[NH4^+][OH^-]}{[NH4OH]} ]

Assuming that the concentration of NH4OH before dissociation is 1.5 × 10^-5 M, we can let x be the concentration of OH- produced after dissociation. The expression then simplifies to:

[ K_b = \frac{x^2}{1.5 \times 10^{-5} - x} ]

At the equilibrium for weak bases, x (the concentration of OH-) is usually small compared to the initial concentration of NH4OH, so we can approximate:

[ K_b = \frac{x^2