Alka Seltzer is an effervescent tablet that contains aspirin (acetylsalicylic ac

Question

Alka Seltzer is an effervescent tablet that contains aspirin (acetylsalicylic acid), citric acid, and sodium bicarbonate (NaHCO3). As soon as the tablet dissolves in water, the NaHCO3 dissociates to form a bicarbonate ion (HCO3-) and a sodium ion (Na+)

1.   NaHCO3(s) --> Na+(aq) + HCO3-(aq)

Acitic acid, which will ‘donate’ H+ to water to create H3O+(aq) is then added to the mixture. With the addition of acetic acid the following acid-base reaction then takes place:

2.   HCO3-(aq) + H+(aq) --> H2O(l) + CO2 (g)

1.Based on your plot (from analysis section). Hint – Consider the reaction equation and vinegar is a source of H3O+ ions.

a) At what range of volumes of vinegar is H+ the limiting reactant?

b) At what range of volumes of vinegar is HCO3- the limiting reactant?

2.   Based on your data and your plot, what is the percent by mass of NaHCO3 in the average Alka Seltzer tablet? Show any calculations used to determine your answer. Remember to average only the HCO3- limited range.

3.    How might this product reduce indigestion or heartburn?

4. Mass can neither be created nor destroyed. If solution decreases in mass where did this “lost” mass go?

5.   Would it be possible to do a similar experiment by measuring the volume of CO2 generated? Explain in detail.

% NaHCO reacted vs acid volume 0 110.0 100.0 O 90.0 z 80.0 70.0 60.0 107.0 102.0 -103,0101.0 104.0 96.6 85.1 64.7 0.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 3 5.0 Volume Acid (mL)

Explanation / Answer

From the above shown plot for the reaction of NaHCO3 in solution with added acetic acid

1. Vinegar is the source of H3O+ ions.

a) Volume of vinegar (range) when H+ is limiting reagent = 0-15 ml

b) Volume of vinegar when HCO3- is the limiting reagent = 15-40 ml

2. Percent mass of NaHCO3 in alka seltzer tablet,

= (102 + 103 + 101 + 107 + 104)/5 = 103.4%

3. Heartburn is casued by excess acid in stomach. The alka seltzer tablet is basic and it reacts with the excess acid and neutralzises it and thus reduce heartburn.

4. The lost mass is formed was water and salt in the system solution.

5. Yes, a similar experiment may be performed by measuring the amount of CO2 formed by decomposition of NaHCO3

NaHCO3 ---> Na+ + HCO3- ---> Na+ + H2O + CO2

Thus by the above shown reaction, we can folow the same with measuring CO2 release.

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