Gravimetric analysis will be used to quantitatively determine the mass of the ac

Question

Gravimetric analysis will be used to quantitatively determine the mass of the active ingredient foun^Mn each antacid. Design the experiment so that 0.5 - 1 g of final product is isolated in each trial. Prepare all solutions at a concentration of 1.0 M or lower and the volume of each solution should not exceed 250 ml. Perform the gravimetric analysis of each antacid in triplicate. It may be necessary to heat samples in the overt for an extended period of time to ensure that they are completely dry. Please plan ahead and be sure the team can come the second lab period to record the mass of the samples. It may be necessary to perform additional experiments only after the final masses are recorded. Be prepared to complete additional lab work as necessary during the second experimental lab period. Sodium bicarbonate is soluble, but calcium carbonate and magnesium hydroxide are not. The two reactions below show how calcium carbonate and magnesium hydroxide can be dissolved in solution. Be sure to record all necessary masses or volumes before doing chemical manipulations. Scheme 1. Reactions of carbonates with hydrochloric acid. CaC03(s) + 2 HC1 (aq) rightarrwo CaCl2 (aq) + C02 (g) + H20(l) Mg(OH)2(s) + 2 HC1 (aq) rightarrow MgCI2 (aq) + 2 H20(1) Although the active ingredient of the Equate Antacid and Milk of Magnesia is soluble in hydrochloric acid, that does not mean everything in the antacid will be. There may be binders or other inactive ingredients in the pill that are not soluble. This holds true for the sodium bicarbonate pill as well (the entire pill may not dissolve). If this happens, the insoluble components can be removed by vacuum filtration using Whatman 42 filter paper and a Buchner funnel. Do not use a glass filter as it may become clogged. Once the active ingredient has been dissolved, it can be precipitated as shown in the reactions below. If the mass of the precipitate is measured, it is possible to back calculate the amount of active ingredient in

Explanation / Answer

1) if you wish to analyze the antacid tablet gravimetrically for Calcium carbonate then you may follow the following steps:

We wish to determine caclium carbonate in the given sample of antacid then we have to precipitate it out by using suitable reagents.

1) Take a well dry preweighed crucible (don weigh the lid with crucible)

2) crush well the antacid table with the help of pestle mortar (crushing ensure better reaction)

3) Take 0.5 g of powdered antacid in the crucible

4) dissolve the powdered antacid tablet in water (with added HCl) [ say 100mL]. reaction will be

CaCO3 + 2H+ --> Ca+2 + CO2(g) H2O

5) now add precipitating agent like ammonium oxalate, dissolved in HCl

(NH4)2C2O4 + 2H+ --> 2NH4+ + H2C2O4

6) Dissolve urea in water and heat the mixture to obtain NH3

7) React the oxalic acid with ammonia (acid base reaction) to obtain oxalate ions

8) react the oxalate ions with the dissolved calcium ion to precipitate out calcium oxalate.

9) Dry the precipitate and weigh it.

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