[Amykin]

I'm stuck on this problem:

What is the pH of a solution when 15.0 mL of a 0.500 M HF solution is added to 15.0 mL of a 0.250 M HCl. Ka for HF is 6.9 x 10^-4

Thank you for any help on how to proceed 

[AWK]

It is sufficient to calculate pH of HCl after dilution. Even in more exact calculations the ionic strength more changes pH than HF.

[tumblewush]

Hey, Amykin 

Yes, as AWK pointed out, just using the information from HCl to calculate pH is enough for this question. This is because HF is a weak acid and so won't dissociate all that much in solution (as indicated by the K_a), and so the [H₃O]⁺ from it is negligible in the calculation. But then if you had to calculate the pH as a requirement, then you'd have to move through this using the ICE method, being wary of initial concentrations of your products.