Calculate the pH of a weak base solution

What is the pH of a 0.25 M weak base solution if the K of the weak base is 1.3 x 10-13?

A. 6.74

B. 8.92

C. 5.06

D. 7.26

Final answer: The pH of a 0.25 M weak base solution is approximately 7.38, so the correct answer is D. 7.26.

To calculate the pH of a weak base solution with a concentration of 0.25 M and a given Kb value of 1.3 x 10-13, we need to follow certain steps.

The first step is to calculate the concentration of hydroxide ions (OH-) in the solution using the equation [OH-] = √((Kb)([HA])) / [A-]. Substituting the values given, we find that [OH-] = 2.42 x 10-7 M.

Next, we calculate the pOH using the formula pOH = -log(2.42 x 10-7), which gives us a value of 6.62.

Finally, the pH can be determined using the formula pH = 14 - pOH, resulting in a pH of approximately 7.38. Therefore, the correct answer is D. 7.26.

Understanding the concepts of weak bases and their equilibrium constants is essential in solving such problems.