Question

The pH of a solution of household ammonia, a 0.950 M solution of (NH₃), is 11.612. Determine (K_b) for (NH₃) from these data.

a) (1.2 × 10⁻5)
b) (2.8 × 10⁻5)
c) (3.7 × 10⁻5)
d) (5.6 × 10⁻5)

Answer 1

To find the Kb for ammonia (NH3) from the given pH, we first calculate the hydroxide ion concentration, and then use it to calculate Kb utilizing the expression Kb = [OH-]^2 / [NH3]. The Kb for NH3 is determined to be 1.76 × 10^-5.

Step-by-step explanation:

To determine the Kb value for ammonia (NH3) from the given pH of 11.612, we first need to calculate the concentration of hydroxide ions (OH-) in the solution. The pH and pOH of a solution are related by the equation: pH + pOH = 14. Therefore, pOH = 14 - 11.612 = 2.388.

The hydroxide ion concentration can be then determined using the formula [OH-] = 10-pOH. After finding the hydroxide ion concentration, we can use the formula Kb = [OH-]2 / [NH3], where [NH3] is the initial concentration of the ammonia which is 0.950 M.

Calculating the hydroxide ion concentration: [OH-] = 10-2.388 = 4.07 × 10-3 M. Now, we use this [OH-] to calculate the Kb for NH3: Kb = (4.07 × 10-3)2 / 0.950 M = 1.76 × 10-5.