Question

Calculate the pH of a 0.25M solution of NH+4 at 25∘C. The Kb of NH3 is 1.8×10^−5.

Report your answer to the hundredths place.

Answer 1

To calculate the pH of a 0.25M solution of NH+4 at 25∘C, you can use the Kb value of NH3, which is 1.8×10^−5. First, write the equation for the ionization of NH+4. Then, use the Kb value to find the concentration of H3O+ ions. Finally, calculate the pH using the formula -log[H3O+].

Step-by-step explanation:

The question asks to calculate the pH of a 0.25M solution of NH4+ at 25°C. To solve this, we can use the Kb value of NH3, which is 1.8×10-5. First, we need to write the equation for the ionization of NH4+ as NH4+ + H2O → NH3 + H3O+. Since NH4+ is the conjugate acid of NH3, it will act as an acid and donate a proton, resulting in the formation of NH3 and H3O+ ions. So, the concentration of NH3 will be equal to the initial concentration of NH4+, which is 0.25M.

Next, we need to find the concentration of H3O+ ions. Since NH4+ is a weak acid, we can assume that only a small fraction of it will ionize. We can use the Kb value to calculate the concentration of H3O+ ions:

Kb = [NH3][H3O+]/[NH4+]

[H3O+] = Kb × [NH4+]/[NH3]

[H3O+] = (1.8×10-5) × (0.25)/(0.25) = 1.8×10-5

The concentration of H3O+ ions is 1.8×10-5 M.

Finally, we can calculate the pH using the formula pH = -log[H3O+].

pH = -log(1.8×10-5) = 4.75.

Therefore, the pH of the 0.25M NH4+ solution at 25°C is 4.75.

Answer 2

To calculate the pH of a 0.25M solution of NH+4, we can use the concentration of NH+4 as the concentration of H3O+ ions. Therefore, the pH is 0.60.

Step-by-step explanation:

To calculate the pH of a solution containing NH4+, we need to determine the concentration of OH- ions. NH4+ is the conjugate acid of NH3, a weak base. It reacts with water to produce NH3 and H3O+ ions. The balanced equation for the reaction is:
NH4+ (aq) + H2O (l) → NH3 (aq) + H3O+ (aq)

From the balanced equation, we can see that the concentration of H3O+ ions is equal to the concentration of NH4+ ions. Given that the concentration of NH4+ is 0.25 M, the concentration of H3O+ ions is also 0.25 M. Since pH is defined as the negative logarithm of the concentration of H3O+ ions, the pH of the solution is -log(0.25) = 0.60.