Hydroxylamine,HONH₂,readily forms salts such as hydroxylamine hydrochloride which are used as antioxidants in soaps.Hydroxylamine has K_b = 9.1 × 10^-⁹.What is the pH of a 0.025 M HONH₂solution? A)2.90 B)4.82 C)9.18 D)9.91 E)11.10

Question

Quizplus · Accepted Answer

Hydroxylamine is a weak base, so it undergoes the reaction HONH2 + H2O ⇋ HONH3+ + OH-. Using the equilibrium constant expression, we can write:

Kb = (HONH3+)(OH-) / (HONH2)

We are given the value of Kb as 9.1 × 10^-9. Let x be the concentration of HONH3+ at equilibrium. Then, the concentrations of OH- and HONH2 will be x and 0.025 - x, respectively. Substituting these values into the expression for Kb, we get:

9.1 × 10^-9 = x(0.025 - x) / (0.025 - x)

Simplifying and solving for x, we get x = 1.53 × 10^-6. Therefore, the concentration of OH- is also 1.53 × 10^-6. Using the equation pH + pOH = 14, we find the pH of the solution to be:

pH = 14 - pOH = 14 - 5.82 = 9.18

Therefore, the correct choice is C.

Hydroxylamine,HONH2,readily Forms Salts Such as Hydroxylamine Hydrochloride Which Are Used

Hydroxylamine,HONH₂,readily Forms Salts Such as Hydroxylamine Hydrochloride Which Are Used