explain how molecular weight of unknown acid would be affected by each of follow
ID: 576070 • Letter: E
Question
explain how molecular weight of unknown acid would be affected by each of following errors
Explain how the calculated molecular weight of the unknown acid would be affected by each of the following experimental errors. In each case you must also state if the calculated molecular weight will be higher or lower than the expected molecular weight. Unknown acid crystals were spilled after being weighed on the analytical balance a. b. Top load balance was used instead of analytical balance The solution of unknown acid was not quantitatively transferred from the beaker to Erlenmeyer flask. c. d. The tip of burette was not filled or had air bubbles. The endpoints were repeatedly overshot. e.Explanation / Answer
We will calculate the molecular mass of unknown acid by knowing its molarity by titrating against known alkali solution.
Molarity =no.of moles/vol of solution in L
And no. of moles= weight of substance/ molecular masa
So molecular mass is inversely proportional to the no. of moles.And no. Of moles are directly to the molarity.
Now cases;
A. This will decrease the conc.of the acidic solution and hence molarity,thus the molecular mass will be higher than the expected.
B.In top load balance some air weight also get weighed with compound and the actual(effective) weight of the compound weighed will be less as shown in the balance as compare to analytical balance .This situation will also have the same effect now as in caseA and the observed molecular mass will be higher than expected.
C.After doing this error we can't calculate the molarity and hence the molecular mass of the unknown acid can't be calculated.
D.This error will decrease the vol. of acid and hence less alkali will used than the expected and hence the molarity of the acidic solution will be a little less than the actual.Thus as no. of moles is directly to molarity and molecular mass is inversely to no. of moles ,so the molecular mass will be higher than the expected.
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