https://www.youtube.com/watch?v=Wj4-nQmW28syou can just type in the document i provided. I have attached answer key as well, so all you need to do is paraphrase. You can take help from video.
.6_answer_key__1_.docx
lab_5.6_questions_for_the_experiment1__1_.docx
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Questions for the experiment:
1. According to the information in the Medline Plus of the National Library of Medicine, What
are the common active ingredients present in commercial antacids?
Ans.: Antacids with aluminum used as the active ingredient includes alumina, aluminum
hydroxide, and basic aluminum carbonate. Antacids with magnesium ion usually contain
magnesia, and magnesium trisilicate, magnesium carbonate, magnesium alginate, magnesium
hydroxide, and magaldrate, Antacid with calcium ion ordinarily has calcium carbonate. Among
these brands, major productions consist of aluminum and magnesium ions.
2. Write out the compound names, molecular formulas, and molecular weights of active
ingredients in antacids.
Ans.: Antacids with aluminum ion include alumina (Al2O3, 101.9); aluminum hydroxide
[Al(OH)3, 78.00]; and basic aluminum carbonate {an aluminum hydroxide–aluminum carbonate
[Al2(CO3)3, 234.00] complex}. Antacids with magnesium ion cover magnesia (MgO, 40.31);
magnesium trisilicate (Mg2Si3O8, 260.85); magnesium carbonate (MgCO3, 84.32); magnesium
alginate (Not found, while sodium alginate, C5H7O4COONa, 216.1); magnesium hydroxide
[Mg(OH)2, 58.32]; and magaldrate (a combination of aluminum hydroxide and magnesium
hydroxide). Antacid with calcium ion has calcium carbonate (CaCO3, 100.09).
3. Why is aluminum ion best determined by complexometric back titration?
Ans.: Complexometric back titration generally performs when the metallic ions form a stable
complex with EDTA in a slow reaction or when a metal ion blocks an indicator. The blocked
indicator cannot release metallic ions, thus no color change will be observable at the endpoint of
complexometric direct titration. Both conditions exist in the case of aluminum ion, thus the ion is
best determined by complexometric back titration along with heating to enhance the
complexation of Al-EDTA.
4. What method is best for the determination of aluminum amount alone in antacid?
Ans.: In this determination, antacid sample solution is controlled in a pH 5.0 buffer solution and
then an excess known amount of EDTA is added. At this low pH, the Al-EDTA complex can
form, whereas the Mg-EDTA complexation is completely inhibited. Heating the mixture prior to
adding indicator xylenol orange is imperative to prevent aluminum ion blocking the indicator
and to facilitate the EDTA-Al complexation. The amount of unchelated EDTA is then back
titrated with standardized zinc solution at the endpoint detection of a change to light red color.
5. What sort of water can be used for this experiment?
Ans.: It is important to use demonized water rather than distilled water for reagents preparation,
sample preparation and rinsing all glassware.
6. What is the weight of the aluminum compound in the antacid you analyzed. Assuming you
used hydrotalcite, Mg6Al2(CO3)(OH)16·4(H2O) (molecular weight = 603.98), as active
ingredient, and added an excess 25.00 mL of 0.01000 M EDTA to a 10.00 mL of antacid sample
solution and then back-titrated it with an 18.41 mL of 0.01000 M standardized zinc solution.
Show calculations.
Ans.: The millimole of aluminum ion in 10.00-mL sample solution is equal to (25.00
mL*0.01000 M) – (18.41 mL*0.01000 M) = 0.0659 millimole. So the aluminum millimole of
250.00-mL sample solution is equal to 0.0659 millimole multiplying by (250.00 mL / 10.00 mL)
= 1.648 millimole. The antacid tablet has 0.9388 g and its powder with 0.9380 g dissolved in
demonized water and diluted to 250.00 mL, so the millimole of aluminum ion in the antacid
tablet is equivalent to 1.648 millimole multiplied by (0.9388 g / 0.9380 g) = 1.649 millimole.
Thus, the weight of hydrotalcite in the tablet is equal to 1.649 millimole multiplied by (603.98 /
2) = 498 mg.
7. From the preceding question 1, compare your own results with declared weight for the active
ingredient in the antacid you analyzed, what is the error percentage?
Ans.: The declared weight of hydrotalcite in the antacid is 500 mg. Thus, I got a small difference
of -2 mg (498 mg – 500 mg) or -0.4% (-2 mg / 500 mg * 100%) between the calculated and
declared values.
8. What would be the effect on the calculated active ingredient values in an antacid
if an insufficient time of boiling the solution in the procedure?
Ans.: This will cause an incomplete formation of Al-EDTA complex and make aluminum ion
blocking the indicator. In this case, complexometric back titration is not completed. No change
in color at the endpoint can be observable so that calculated value of active ingredient become
very small.
Questions for the experiment:
1. According to the information in the Medline Plus of the National Library of Medicine, What
are the common active ingredients present in commercial antacids?
Ans.:
2. Write out the compound names, molecular formulas, and molecular weights of active
ingredients in antacids.
Ans.:
3. Why is aluminum ion best determined by complexometric back titration?
Ans.:
4. What method is best for the determination of aluminum amount alone in antacid?
Ans.:
5. What sort of water can be used for this experiment?
Ans.:
6. What is the weight of the aluminum compound in the antacid you analyzed. Assuming you
used hydrotalcite, Mg6Al2(CO3)(OH)16·4(H2O) (molecular weight = 603.98), as active
ingredient, and added an excess 25.00 mL of 0.01000 M EDTA to a 10.00 mL of antacid sample
solution and then back-titrated it with an 18.41 mL of 0.01000 M standardized zinc solution.
Note: Your antacid tablet total weight is 0.9380 grams and is diluted in 250 mL’s of DI H20
Show calculations.
Ans.:
7. From the preceding question 1, compare your own results with declared weight (500 mg
Hydrotalcite) for the active Ingredient in the antacid you analyzed, what is the error
percentage?
Ans.:
8. What would be the effect on the calculated active ingredient values in an antacid
if an insufficient time of boiling the solution in the procedure?
Ans.:
…
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