10.00 mL of an unknown base solution is titrated with .100 M HCl solution. The pH versus the volume of NaOH added is shown below.

There is a graoh where there are two dotted lines signifying a pH: the highest at pH 6.31 and the lower at pH 3.92.

What is the pOH pf the solution at half equivalence point?
What is the ionization constant, Kb, for the unknown base?

I'm confused. You have an unknown base, you're titrating with HCl, and you're adding NaOH? Something strange in Denmark.

To find the pOH of the solution at the half-equivalence point, we need to first understand what the half-equivalence point is. In a titration, the half-equivalence point occurs when exactly half of the base has reacted with the acid.

From the given information and graph, we can see that the pH at the half-equivalence point is 6.31. Remember that pH and pOH are related, and the sum of pH and pOH is always equal to 14. Therefore, we can find the pOH by subtracting the pH from 14.

pOH (at half-equivalence point) = 14 - 6.31 = 7.69

So, the pOH of the solution at the half-equivalence point is 7.69.

Moving on to finding the ionization constant (Kb) for the unknown base, we need to know the concentration of the base at the half-equivalence point. This information can be obtained from the volume of HCl solution added at the half-equivalence point.

Once we know the volume of HCl added, we can calculate the moles of HCl, since we know the concentration of the HCl solution. As the base and acid react in a 1:1 ratio, the moles of the base will be equal to the moles of the acid at the half-equivalence point.

Next, we divide the moles of the base by the volume of the base solution to obtain the concentration of the base at the half-equivalence point.

Lastly, we can construct an ICE table using the concentration of the base at the half-equivalence point. From this table, we can calculate the ionization constant (Kb) for the unknown base.

The Kb is defined as follows:

Kb = [OH-]^2 / [Base]

By substituting the calculated values into this equation, we can find the ionization constant, Kb, for the unknown base.