Question

A 1.2 M solution of a weak base B is prepared. Using a pH meter, the pH is measured to be 11.82. Calculate the base ionization constant

Answer 1

Kb = 3.64x10⁻⁵

Step-by-step explanation:

First we calculate the pOH of the solution:

• pOH = 14 - pH

• pOH = 2.18

Then we calculate [OH⁻]:

• pOH = -log[OH⁻]

• [OH⁻] =
  `10^(-pOH)`

• [OH⁻] = 0.0066 M

For a weak base solution with a relatively high concentration, we can use the following formula:

• [OH⁻] =
  `√(Kb*C)`

Where C is the concentration of the weak base solution (1.2 M in this case).

With the formula above we can calculate Kb:

• 0.0066 =
  `√(Kb*1.2)`

• Kb = 3.64x10⁻⁵