Question

Determine the equilibrium concentration of the base NH₃ given that pKb=4.76 and the equilibrium concentrations of OH⁻ and NH⁺⁴ are 6.5×10⁻⁵ M, and 0.42 M respectively.

Answer 1

The equilibrium concentration of NH3 is calculated using Kb and the provided concentrations of NH4+ and OH-. Rearranging the base dissociation constant equation and substituting the given values results in a concentration of approximately 1.4x10^-2 M for NH3.

Step-by-step explanation:

To determine the equilibrium concentration of the base NH3 when given pKb=4.76 and the equilibrium concentrations of OH− and NH4+ are 6.5×10−5 M, and 0.42 M respectively, we can use the expression for the base dissociation constant Kb. The base dissociation of NH3 is represented as NH3(aq) + H2O(l) → NH4+(aq) + OH−(aq). The base dissociation constant Kb is calculated as such:

Kb = [NH4+][OH−] / [NH3]

Rearranging to solve for [NH3], we get:

[NH3] = [NH4+][OH−] / Kb

Using the given values:

[NH3] = (0.42 M)(6.5×10−5 M) / (10−4.76)

Calculating this, we find the equilibrium concentration of NH3 to be approximately 1.4×10−2 M.