Question

What is the pH of a 0.200 M CH3NH3Br solution? Kb of CH3NH2 = 4.4 × 10−4

Answer choices
a. 5.47
b. 5.67
c. 8.32
d. 8.53

Answer 1

The pH of a 0.200 M CH3NH3Br solution can be calculated using the Kb value of CH3NH2. The pH is approximately 11.96.

Step-by-step explanation:

The pH of a solution can be calculated based on the concentration of the acid or base and the equilibrium constant. In this case, we can calculate the pH of a 0.200 M CH3NH3Br solution using the Kb value of CH3NH2. First, we need to find the concentration of CH3NH2 by considering the reaction:

CH3NH3+ + H2O ↔ CH3NH2 + H3O+

From the reaction, we can see that the concentration of CH3NH2 is equal to the concentration of CH3NH3+ and can be calculated as:

[CH3NH2] = [CH3NH3+] = 0.200 M

Next, we can use the Kb value of CH3NH2 to calculate the concentration of OH- ions:

[OH-] = sqrt(Kb * [CH3NH2])

Plugging in the values, [OH-] = sqrt(4.4 x 10^-4 * 0.200) = 0.0094 M

Finally, we can use the concentration of OH- to solve for the concentration of H3O+ and calculate the pH:

[H3O+] = Kw / [OH-] = 1.0 x 10^-14 M / 0.0094 M = 1.1 x 10^-12 M

pH = -log[H3O+] = -log(1.1 x 10^-12) ≈ 11.96

Therefore, the correct answer is not listed in the answer choices provided. It is approximately 11.96.