How many moles of CO2 are produced from one Alka-Seltzer tablet?

Answer 1

Hi there,

So Alka Seltzer is composed primarily of Sodium Bicarbonate (NaHCO₃) and Citric Acid (H₃C₆H₅O₇). When it is placed in water, the following reaction occurs (already balanced):

H₃C₆H₅O₇(aq)+3NaHCO₃(aq)→3CO₂(g)+3H₂O(l)+Na₃C₆H₅O₇(aq)

Per the drug label from Bayer, the by mass ratio of the ingredients per tablet is 1000mg Citric Acid, 325mg Aspirin, and 1916mg Sodium Bicarbonate.

1. We first need to find the molecular weights of either citric acid and sodium bicarbonate in order to find the number of moles that will be reacting. This will also help us to find which of the two is the limiting reagent. The molecular weight of citric acid is 192g/mol and for sodium bicarbonate is 84g/mol. Thus, one tablet of Alka-Seltzer has approximately 0.0052 moles of citric acid and 0.0228 moles of sodium bicarbonate.
2. Since the balanced chemical reaction requires 3 moles of sodium bicarbonate for every mole of citric acid, reacting 0.0052 moles of citric acid would require 0.0156 moles of sodium bicarbonate. As this is less than the total moles of sodium bicarbonate present, the citric acid is our limiting reagent.
3. We now use the balanced chemical reaction to determine how many moles of carbon dioxide will be produced. As citric acid and carbon dioxide are in a 1:3 ratio in the chemical equation, 0.0052 moles of citric acid will result in 0.0052*3, or 0.0156 moles of carbon dioxide.