I can find the initial pH of the solution, but I am not given any initial volumes so can you point me in the right direction of how to solve this problem? If I don't need volumes can you give me a hint as to how this problem should be solved?
You can do this only by considering the proportions of acid and alkali. Given the concentrations, the equivalence point will be when the volume of added alkali is 50% of the initial volume of acid. With 25% alkali we find the half-neutralized point where the pH = pKa (i.e 4.76 for this acid). You have already found the pH at ...
This solution provides a detailed response which indicates how this problem can be solved when the volumes in the experiment are unknown. This is done in about 250 words.