Experiment 11 Determination of Sodium Bicarbonate in Alka-Seltzer Use the follow
ID: 704074 • Letter: E
Question
Experiment 11 Determination of Sodium Bicarbonate in Alka-Seltzer Use the following data obtained in the analysis of an Alka-Seltzer tablet to make the calculations asked for. They parallel those in the experiment to be performed. See the sequence of calculations given in the Data and Calculations sheet for helpful hints. Data Mass of whole tablet Mass of half-tablet taken for reaction Volume of CO2 + water vapor (corrected) Temperature of gas Vapor pressure of water at 22.0°C Barometric pressure, corrected Calculations (Show your work.) 1. partial pressure ofco, 3.478 g .973 g 314 mL 22.0°C 21 torr 757 torr 2. moles of CO2 3. moles of NaHCO 4. mass of NaHCO3 5, mass % NaHCO3 in Alka-Seltzer 6. mg of NaHCOs per one tablet, calculated On its label, the company (Miles Laboratories) claims 1904 mg NaHCO; per tablet. Taking this to be the true value, what is the % error in the above experimental work?Explanation / Answer
Partial pressure of CO2 = Barometric pressure - Vapor pressure of water
= 757 - 21
= 736 torr
P = 736 torr x 1 atm/760 Torr = 0.9684 atm
From the ideal gas equation
Moles of CO2 = PV/RT
= 0.9684 atm x 0.314 L / 0.0821 L-atm/mol-K x (22+273)K
= 0.01255 mol
The reaction
NaHCO3 + HCl = NaCl + CO2 + H2O
Moles of NaHCO3 consumed = moles of CO2 produced
= 0.01255 mol
Mass of NaHCO3 = moles x molecular weight
= 0.01255 mol x 84 g/mol
= 1.0542 g
Mass% NaHCO3 = mass of NaHCO3 x 100 / mass of half tablet taken
= 1.0542 x 100 / 1.973
= 60.62 %
mg of NaHCO3 per tablet = 3.478 x 0.6062
= 2.108 g x 1000mg/g = 2108 mg
% error = (2108 - 1904)*100/1904 = 10.71 %
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