Assume the standardized NaOH used for the titration of benzoic acid had a concen
ID: 509537 • Letter: A
Question
Assume the standardized NaOH used for the titration of benzoic acid had a concentration of 0.2301 M. Further assume you did not write down this exact concentration immediately but later tried to from memory and incorrectly wrote down 0.2 M. How might this affect your results?
This assumption would increase the moles of acid calculated.
This assumption would result in a larger calculated molecular weight for benzoic acid.
This assumption would result in a smaller calculated molecular weight for benzoic acid.
This would have no effect on the results.
None of the answers shown are correct.
Explanation / Answer
Ans: This assumption would result in a larger calculated molecular weight for benzoic acid.
Explanation: We know Number of moles of NaOH used will be volume times the molarity. We then find by titration the amount of NaOH consumed. Using this calue we try to estimate the molarity of the benzoic acid. And then we know volme and molarity so we calculate the moles of benzoic acid used. Then we know how much benzoic acid we had added so we arrive at the molecular weight by using formula Moles = Mass / Molecular Weight. Now if we had incorrectly written the Molarity of NaOH as 0.2 M in place 0.2301M then this means we will assume less number of mles of NaOH were used and there by implying that there are less number of moles of Benzoic acid. Now we know how much benzoic acid was added. Hence then try to find M.W. but as the number of moles calculated are less hence we arrive at the M.W. which is greater than the actual one.