A student standardizes a solution of Na2S2O3 by titrating it against a solution containing a known m — Laboratory Chemistry Question
Question
A student standardizes a solution of Na2S2O3 by titrating it against a solution containing a known mass of NaIO3 that has been dissolved in an excess of a freshly prepared solution of KI in dilute HCl. Which of the following errors will lead to a value of the molarity of the thiosulfate solution that is higher than the true value?
A.
The student overshoots the endpoint of the titration.
B.✓ Correct
The NaIO3 is contaminated with NaCl.
C.
The KI/HCl solution is allowed to stand overnight before it is used in the titration.
D.
The sample of sodium thiosulfate pentahydrate used to make the Na2S2O3 solution had partially dehydrated on standing.
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