PH of solution from mixing four solutions

[MightyMan11]

Homework Statement

What is the pH of the solution that results from mixing the following four solutions together:
(i) 150 ml of 0.250M NaCl
(ii) 300 ml of 0.200M HCl
(iii) 100 ml of 0.050M HNO₃
(iv) 450ml of 0.200M NaOAc

Homework Equations

The Attempt at a Solution

Firstly, NaCl does not contribute to the pH of the solution.
HCl and HNO₃ are both strong acids and contribute 0.065 mol of hydronium.
There are also 0.09 mol of NaOAc (weak base) in the solution.
The hydronium reacts with NaOAc, resulting in 0.025 mol of NaOAc in a 1L solution (0.025M NaOAc).

Setting up an ICE table for acetate and acetic acid and using Kb for acetate is equal to 5.56x10^-10 i worked out that the concentration of OH was 3.73x10^-6.
Then -log[OH] resulting in pOH of 5.43,
pH of 8.57

However, my answer is not in the choices that are given to me.
choices:
4.22
4.33
2.74
4.98
5.16

can anyone help?
thanks

 

[Borek]

0.065M of hydronium
0.09M of NaOAc

Once they react, you have a solution containing both acetic acid and its conjugate base. Such a solution has a name and its pH is described by specific equation. ICE table is useless here.

 

[MightyMan11]

Thanks.
I had completely forgotten about the acetic acid that forms.