Instructor Nane: Student Name: EXP #6 POST-LAB: 1. Missy Mae is in a hurry to ge

Question

Instructor Nane: Student Name: EXP #6 POST-LAB: 1. Missy Mae is in a hurry to get home and watch reruns of The Walking Dead, in her haste; she deviates from the experimental procedure in several ways. Explain how these would affect the outcome of the end result, number of milligrams of iron in the tablets. Would these sway the result erroncously higher, lower, or make no change? Explain. a) During the standardization of the KMnOs portion, she weighs all the FAS but spills a portion of it on the lab counter, never adding the full amount to the titration flask. b) There is a bubble in the buret containing the KMnO4 solution, which comes out unnoticed during part 3 of the experiment; the titration of the iron tablets. 2. Why did you add sulfuric acid to each sample titrated? 3. On a bottle of iron supplement the facts list on the label states the following: "Ingredients: Dried ferrous sulfate 202 mg (equivalent to 325 mg Liquid Ferrous Sulfate which provides 65 mg elemental iron per tablet)" Use your knowledge of % composition of compounds to prove disprove the above statement through calculation (hint: how much iron is there in ferrous sulfate (a.k.a. iron (II) sulfate)?). 13 CHE-1251 Experiment 6

Explanation / Answer

1. a. The Spilled FAS will defenitely alter the Normality or molarity of the KMnO4 solution during standardisation which will indirectly alter the results. The end result of standardisation i.e the normality or molarity of KMnO4 will decrease due to the spillage of FAS. Where the weight of FAS is used in calculating the nomality of KMnO4.(for example if the normality of KMnO4 after standardisation was supposed to be 0.1N but due to spillage of FAS it might come out to be less than 0.1 N). When actually the normality is less and used for the titration of Iron tablets. The B.R will come out more and it will give higher Elemental iron content.

1.b. The air bubble will result in giving higher B.R which will give higher Elemental iron content.

2.KMnO4 titrations (redox titrations ) require acidic medium, hence sulphuric acid is added during titration. It increases the concentration of hydrogen ions in the solution. HCl cant be used as Cl- ions get oxidised to free Chlorine and permanganate ions will not be available for further titration.

3. Theoretically 278.02 mg of Liq FeSO4 contains 56 mg of Fe

325 mg of Liq FeSO4 contains 65 mg of Fe

Theoretically 169.93 mg of dried FeSO4 contains 56 mg of Fe

202 mg of dried FeSO4 contains 66.37 mg of Fe

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

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