A 0.035 M solution of a weak base has a pH of 10.88. What is the Kb for the acid?

Where Di I even begun**???

You ALWAYS start with one or all of the following:

1. balanced equation
2. ICE chart
3. think in terms of mols.

pH = 10.88 so pOH = 3.12 and OH^- = 7.58E-4
M..........BOH ==> B^+ + OH^-
initial.0.035M.....0......0
change..7.58E-4..7.58E-4..7.58E-4
equil..0.035-7.58E-4....etc

Kb = (B^+)(OH^-)/(BOH)
Substitute from the ICE chart and solve for Kb. Note that 0.035-7.58E-4 is not = 0.035

To determine the Kb for the acid, we need to first identify the weak base. Then, we can use the pH of the solution to calculate the concentration of hydroxide ions (OH-) and subsequently determine the concentration of the weak base. Finally, we can use the concentration of the weak base to calculate Kb.

Here's the step-by-step process to solve the problem:

1. Identify the weak base: In this case, we are given a 0.035 M solution of a weak base.

2. Calculate the concentration of hydroxide ions (OH-): Since the pH is given, we can use the formula pH = -log[H+]. Rearranging the formula gives [H+] = 10^(-pH). Since pH = 10.88, [H+] = 10^(-10.88). Since water dissociates into H+ and OH- ions, [OH-] is equal to [H+]. Therefore, [OH-] = 10^(-10.88) M.

3. Calculate the concentration of the weak base: Since the solution is a 0.035 M solution of the weak base, [weak base] = 0.035 M.

4. Write the reaction of the weak base with water: The reaction can be written as follows:
weak base + H2O ↔ conjugate acid + OH-

5. Set up an ICE table (Initial, Change, Equilibrium) for the reaction: Let's assume x is the concentration of OH- produced by the weak base.

Initial: 0.035 M 0 M 0 M
Change: -x M -x M +x M
Equilibrium: 0.035 - x M -x M x M

6. Write the expression for Kb: Kb = [conjugate acid][OH-] / [weak base]

7. Calculate Kb: The concentration of the conjugate acid is equal to x, so Kb = x * x / (0.035 - x).

8. Use the pH value to solve for x: Since Kb can be considered small compared to the initial concentration of the weak base (0.035 M), we can assume that x is a small value compared to 0.035. Therefore, we can approximate 0.035 - x ≈ 0.035.

Using Kb = x * x / (0.035 - x) and [OH-] = 10^(-10.88), we can solve the equation by substituting the given values and solving for x.

9. Calculate Kb using the value of x obtained in the previous step.

By following these steps, you can calculate the Kb for the acid.