6. (5) When solutions of sodium thiosulfate, Na S Os, are standardized using pot

Question

6. (5) When solutions of sodium thiosulfate, Na S Os, are standardized using potassium iodate, KIOs, reacted with HCI and excess KI, iodine is produced by the reaction: IO (aq) +5 I(aq) + 6 H'(aq)312(a) 3 H20 12(aq) + 2SzO32(aq) 21(aq) +SO62-(aq) The resulting iodine is titrated to a starch endpoint with the thiosulfate solution: If the titration is not performed quickly, additional I2 is produced by the oxidation of I by O2 in the air: 41(aq) +O2(g) + 4H'(aq) 212(aq)+2H2O. Explain what effect this error would have on the calculated concentration of the thiosulfate solution. Explain whether this type of error would be random or systematic.

Explanation / Answer

If titration is not performed quickly, more amount of I2 will be produced. Thus the concentration of I2 will be more than we note down in our lab copy. Hence, more volume of Na2S2O3 solution will be required to reach the end-point compared to the original value. Thus, the value reported will have error.

These errors can be termed as systematic error which resulted due to flaw in the experiment.

Related Questions

Navigate

• Browse (All)
• Browse 6
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.