What is the pH of a buffer solution with known concentrations of HClO and NaClO?

[Xels]

Homework Statement

A 100.0mL buffer solution is 0.175M in HClO and 0.150M in NaClO.
Find the pH of the solution.

Homework Equations

Ka=10^-pH
([H30+][A-])/([HA])
-log([H30+]) = pH

The Attempt at a Solution

[HClO] [H3O+] [ClO-]
I .175 0 .150
C -x +x +x
E .175-x x .150+x

([x][.150+x])/([.175-x])
([x][.150])/([.175]) (assuming x is small)

This is where I'm stuck; having neither a pH nor Ka/Kb values. The homework is setup in such a way that we aren't expected to find known values from outside sources and none are provided in the text or in any previous problem sets. Because of this I'm assuming that there should be a way to find the hydronium concentration and/or the Ka, but I can't figure out how.

 

[Borek]

This is where I'm stuck; having neither a pH nor Ka/Kb values. The homework is setup in such a way that we aren't expected to find known values from outside sources and none are provided in the text or in any previous problem sets. Because of this I'm assuming that there should be a way to find the hydronium concentration and/or the Ka, but I can't figure out how.

If you are not allowed to check the Ka value there is no way of solving the problem. Period. pH of a solution containing a weak acid and its conjugate base is a function of Ka.

Look for pKa and use Henderson-Hasselbalch equation. That's the simplest (and only realistic) way of solving the question.

 

[Xels]

Thank you; this is the point I was getting hung up on. Knowing that I'm not expected to deduce the Ka I'm willing to resort to known values.