Lindsey Stockton. 3/2/2013. Section 16093.
Determination of % by mass of NaCO3 in Alka-Seltzer Tablets
Alka-Seltzer is an effervescent antacid typically used for pain relief and neutralizing stomach acid to alleviate indigestion. Alka-Seltzer tablets contain Aspirin, Citric Acid (CH3COOH), and Sodium Bicarbonate (NaCO3). When the tablet is placed in water it undergoes an acid-base reaction and Carbon Dioxide (CO2) is a byproduct that causes the notorious “Fizz”. The objective of the lab was to measure the % of NaCO3 in an Alka-Seltzer tablet in different measures of an acidic solution (Vinegar). Through understanding of stoichiometric relationships and limiting reactants, quantities of substances yielded or consumed in a reaction can be determined by analyzing the amount of material involved. A vinegar-water solution is employed in this experiment because a fixed amount of NaCO3 can be reacted in pure water, by manipulating the amount of vinegar in the dissolving solution, the amount of acid capable of reacting increases; resulting in a greater amount of NaCO3 reacted and greater generation of CO2. Percent by mass of NaCO3 that has reacted can be determined by using mass difference and dimensional analysis to relate the amount of CO2 produced to the amount NaCO3.
Collective class data are exhibited in Table 1, and Figure 1 renders the class findings in a plot. As shown in Figure 1, the percent by mass of Sodium Bicarbonate in the Alka-Seltzer tablet primarily increased along with the volume of vinegar used then began to equalize after 15 mL of vinegar was used. In the portion of the graph prior to the trial using 15 mL of vinegar, the acid was the limiting reactant. Initially as additional quantities of vinegar were added, there was more acid available to react with the NaCO3; which is a standard and constant in every tablet of Alka-Seltzer. This resulted in greater production of CO2, thus the percent by mass of Sodium Bicarbonate increased with an...
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