This looks like a home work question. So, I am going to tell you how to figure out the answer rather than give it to you. First of all, you need to ask yourself what you need to get the answer. The answer for which we are looking is the molar mass. This means that we need to know how many grams per mol the acid is. In other words, we need to know the mass of one mol of the acid. Ok, so now that we know what we need, we can take a look at what we have and try to figure out how to get what we need from this. What we have is the mass of a sample of the acid (2.867 g), we are told that it is a monoprotic acid, and we are told how many mols of NaOH is required to neutralize it. The key here is that we are told that it is a MONOprotic acid. This means that releases a single proton (H+ ion) into solution when it disassociates. Note also that NaOH releases a single OH- ion into solution when it disassociates. Now let me give you a few additional questions that when answered should lead you to the correct answer. 1. Given that this acid releases 1H+ per molecule and the NaOH releases 1OH- per molecule, what is the ratio between the number of mols of acid present in the solution to the number of mols of NaOH used to neutralize it? 2. If you have answered the previous question correctly, then you should know the number of mols of acid that is present. Given this and the mass of the sample that you are given, how do we calculate the grams per mol? If you have answer question 2 correctly, then you now know all that you need to get the correct answer to your question. If you will now leave your answer and/or any other questions about this that you may have as a comment on this answer, then I will get back to you with more help as soon as I can.