This question is asking for the pH of a buffer solution between ammonia and nitric acid, with given volumes and concentrations. At the end, the result turns out to be 10.488.
<h3>Buffers</h3>
In chemistry, buffers are known as substances attempting to hold a relatively constant pH by mixing and acid and a base (weak and strong). In such a way, for the substances given, the first step will be to calculate the consumed moles as they are mixed:

Now, since ammonia is in a greater proportion, one can calculate how much of it is left after being consumed by the nitric acid:

And its new concentration:
![[NH_3]=\frac{0.001mol}{0.1L+0.09L} =0.00526M](https://tex.z-dn.net/?f=%5BNH_3%5D%3D%5Cfrac%7B0.001mol%7D%7B0.1L%2B0.09L%7D%20%3D0.00526M)
Next, with ammonia's ionization:

We set up the equilibrium expression based on ammonia's Kb:
![Kb=\frac{[NH_4^+][OH^-]}{[NH_3]}](https://tex.z-dn.net/?f=Kb%3D%5Cfrac%7B%5BNH_4%5E%2B%5D%5BOH%5E-%5D%7D%7B%5BNH_3%5D%7D)
Which can be solved by introducing x and using ammonia's Kb:

Then, we solve for x which is also equal to the concentration of ammonium and hydroxide ions in the solution:

Ultimately, we calculate the pOH and then turn it into pH with:

Learn more about buffers: brainly.com/question/24188850