Question

What is the actual concentration of molecular nh3 in a 0.400 m solution of ammonia? The kb value for ammonia is 1.80 x 10⁻⁵.

Answer 1

The actual concentration of molecular NH₃ in a 0.400 M solution is 0.389 M.

Step-by-step explanation:

To determine the actual concentration of molecular NH₃ in the solution, we need to consider the dissociation of ammonia in water. Ammonia (NH₃) is a weak base, and it undergoes partial ionization in water, represented by the equilibrium equation:

The given Kb value (1.80 x 10⁻⁵) corresponds to the equilibrium expression:

Given that the initial concentration of NH₃ is 0.400 M, and assuming x as the change in concentration due to dissociation, we can set up an ICE (initial, change, equilibrium) table and solve for the equilibrium concentration of NH₃.

After solving, we find that the equilibrium concentration of NH₃ is approximately 0.389 M. This represents the actual concentration of molecular NH₃ in the 0.400 M solution after considering the partial ionization. Understanding the dissociation of weak bases is crucial in calculating the true concentration of the molecular species present in a solution and is a fundamental concept in the study of acid-base chemistry.

Answer 2

The actual concentration of molecular NH3 in a 0.400 M solution of ammonia is 8.49 x 10^-4 M.

Step-by-step explanation:

The actual concentration of molecular NH3 in a 0.400 M solution of ammonia can be calculated using the equation:

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

To find the actual concentration, we need to calculate the hydroxide ion concentration (OH-) using the Kb value of ammonia. The Kb value is 1.80 x 10^-5. We can use the equation Kb = [NH4+][OH-]/[NH3] to solve for [OH-].

Let x be the concentration of OH-. Then, since the moles of NH4+ and OH- are equal, the concentrations of NH4+ and OH- will both be x. The concentration of NH3 is 0.400 M, so we can substitute the values into the equation:

1. 1.80 x 10^-5 = (x)(x)/(0.400)
2. 1.80 x 10^-5 = x^2/0.400
3. x^2 = (1.80 x 10^-5)(0.400)
4. x^2 = 7.2 x 10^-6
5. x = sqrt(7.2 x 10^-6)
6. x = 8.49 x 10^-4

The actual concentration of molecular NH3 in the 0.400 M solution of ammonia is 8.49 x 10^-4 M.