Question

The dissociation constant for ammonia is K_b =___. If equilibrium concentrations of NH₄ and OH⁻ are each 2×10^−3 M and wthe concentration of NH₃ is 0.2 M, what is K _b forammonia?

Answer 1

The dissociation constant (Kb) for ammonia is 2×10−5, calculated using the given equilibrium concentrations of NH4+, OH−, and NH3.

Step-by-step explanation:

To calculate the dissociation constant (Kb) for ammonia (NH3), we can use the equilibrium concentrations of the products and the reactant in the following base ionization reaction:

NH3 + H2O ⇌ NH4+ + OH−

The base ionization constant expression for this equilibrium is:

Kb = [NH4+][OH−] / [NH3]

Given the equilibrium concentrations, we can substitute them into the equation:

Kb = (2×10−3 M)(2×10−3 M) / 0.2 M = 4×10−6 / 0.2 M

Kb then simplifies to 2×10−5.

So, the dissociation constant Kb for ammonia is 2×10−5.