This just answers your question but I didnt really look at the actual problem.
I think I understand what they are asking and if so, it seems like they are nit picking a little. But I could be way off. You have carboxylate in your solution due to the presence of -OH. Now you have a symmetrical carboxylate, COO-, and now you will see two bands, symmetrical and asymmetrical. The resonance hybrid now has a bond order between 1 and 2, and the stretch frequencies of C-O (bond order 1) is ~1100 and C=O (bond order 2) is ~1700. Which makes sense that the ratio between the two frequencies is 1/(square root 2) according to the quantized harmonic oscillator model. Our predicted stretch frequency is somewhere between these two values. The asymmetrical one is going to be higher than the symmetrical. It should be at least below 1600 I think.
