Question

The fizz produced when an Alka-Seltzer® tablet is dissolved in water is due to the reaction between sodium bicarbonate (NaHCO3) and citric acid (H3C6H5O7): 3NaHCO3(aq)+H3C6H5O7(aq)→3CO2(g)+3H2O(l)+Na3C6H5O7(aq) In a certain experiment 1.50 g of sodium bicarbonate and 1.50 g of citric acid are allowed to react. B How many grams of carbon dioxide form? C How many grams of carbon dioxide form?

Answer 1

The balanced equation is

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

B and C are asking for CO2 only. In order to find this first, we have to find the number of moles of sodium bicarbonate and citric acid present in the solution.

molar mass of citric acid is 192.124 g/mol

number of moles of citric acid used for the reaction = 1.5/192.124 =0.0078 moles

molar mass of NaHCO3 is 84 g/mole

number of moles used for the reaction = 1.5/84 = 0.0178 moles

From the balanced chemical equation, it is clear that one mole citric acid react with 3 moles NaHCO3

The ratio of moles of NaHCO3 to citric acid = 2.28

ie NaHCO3 is less in number of moles and it acts as the limiting reagent.

Also, from balanced equation, it is clear that 1 mole NaHCO3 produces 1 mole CO2

0.0178 moles NaHCO3 produces 0.0178 moles CO2

mass of CO2 = number of moles * molar mass = 0.0178 * 44 = 0.7832 g

0.7832 g of CO2 is formed in the reaction