Abi Lundblad
Chem&163
Due: April 30th, 2025
Analysis of Antacids
Purpose
Determine the number of moles of acid neutralized per tablet and the cost analysis per
tablet through a technique called back titration. The number of moles of HCl neutralized by the
antacid is the difference in moles of HCl initially present and the excess moles of HCl titrated by the
NaOH. Additionally, we will calculate the cost per tablet based on moles of neutralization potential.
Data
Antacid Brand: Equaline
Ingredient Name: Calcium Carbonate
Antacid Tablet Mass: 1.3114g
Ingredient Amount: 500mg
[NaOH] = 0.1068M
[HCl] = 0.2070M
pH = 1
Initial Volume NaOH (mL)
Trial 1
0.200mL
Trial 2
1.60mL
Trial 3
0.50mL
Final Volume NaOH (mL)
34.51mL
35.05mL
34.70mL
Volume NaOH Added (L)
0.03431L
0.3345L
0.03420L
Total Volume HCl (mL)
25.0mL
25.0mL
25.0mL
Antacid Powder Mass (g)
0.2008g
0.2014g
0.2001g
Data Analysis
Equation 1
HClneutralized = HClinitial – HCltitrated
1. HCl Initial
Moles HCl = M x V = 0.005175mol
2. HCltitrated
Trial
1
2
3
Moles NaOH (MNaOH x VNaOH Added)
Moles HCltitrated (1:1 ratio)
0.003664mol
0.003572mol
0.003653mol
0.003664mol
0.003572mol
0.003653mol
3. HClneutralized
Trial
HClneutralized = (HClinitial – HCltitrated)
1
0.001511mol
2
0.001603mol
3
0.001522mol
4. HClentire tablet
Trial
Total Moles in Tablet = (trial moles/trial mass) x total mass
1
0.009866mol
2
0.010435mol
3
0.009978mol
5. Average & Standard Deviation
Average HClentire tablet = 0.010093mol
Standard Deviation = 0.0003103
6. HCltheoretical
CaCO3 (s) + 2 HCl (aq)  CaCl2 (aq) + H2O (l) + CO2 (g)
Moles HCltheoretical = 0.500g CaCO3 x (1mol CaCO3/100.087g) x (2mol HCl/1mol CaCO3)
Moles HCltheoretical = 0.00999mol
7. Percent Error
Percent Error = (|theoretical – experimental|/theoretical) x 100
Percent Error = (|0.00999mol – 0.010093mol|/0.00999mol) x 100 = 1.016%
8. Cost-Analysis
$3.39/bottle (96 count)
Cost per tablet = $0.035/tablet
Cost per mole HClexperimental = $3.50
Cost per HCltheoretical = $3.53
Discussion Questions
1. Summary Table
Average Moles HClexperimental Per Tablet
0.010093mol HCl
Average Moles HCltheoretical Per Tablet
0.00999mol HCl
Standard Deviation
0.0003103
Percent Eror
1.016%
2. The standard deviation for the three trials was 0.003103, which is well within acceptable
statistical limits, meaning all the data we gathered was very similar in value and is clustered
closely around the mean. There were no outliers in the data points.
3. The percent error of 1.016% is well within an acceptable range. The determined Moles
HClexperimental = 0.010093mol HCl was very close to the Moles HCltheoretical = 0.000999mol HCl,
resulting in a very small percent error and therefore validates the accuracy of the data.
4. No, I would not claim the manufacturer’s label is false because the percent error is only
1.016%, which is very small. A consistent error that could explain the slight difference might
be a slight over-titration during the adding of NaOH (mL).
5. Analyzing another brand:
a. Aluminum hydroxide = 160mg
Al(OH)3 (s) + 3HCl (aq)  AlCl3 (aq) + 3H2O (l)
0.160g Al(OH)3 x (1mol Al(OH)3/78.004g Al(OH)3) x (3 mol HCl/1 mol Al(OH)3)
Moles HCltheoretical = 0.006154 mol HCl
Magnesium Carbonate = 105mg
MgCO3 (s) + 2 HCl (aq)  MgCl2 (aq) + H2O (l) + CO2 (g)
0.105g MgCO3 x (1 mol MgCO3/84.32g MgCO3) x (2 mol HCl/1 mol MgCO3)
Moles HCltheoretical = 0.002491mol HCl
Total Moles HCltheoretical = 0.006154mol HCl + 0.002491mol HCl
Total Moles HCltheoretical = 0.008644mol HCl
b. Gaviscon is $9.64/bottle (100 count)
Cost per tablet = $9.64/100 = $0.0964/tablet
Cost per mole HCltheoretical = $0.0965/tablet / 0.008643mol HCltheoretical
Cost per mole HCltheoretical = $11.15/mol HCltheoretical
6. Equaline gives you a better bang for your buck compared to Gaviscon, Equaline cost
$3.53/mol HCltheoretical while Gaviscon costs $11.15/mol HCltheoretical
Conclusion
In this experiment, the average number of moles of HCl neutralized per Equaline table was
0.010093 mol, with a standard deviation of 0.0003103, indicating the data was consistent and
clustered closely around the mean. The percent error between the experimental and theoretical
values was 1.016%, which falls well within an acceptable range for laboratory experimental
(typically under 5% is considered acceptable.) This shows that the results were both accurate and
precise.
A possible source of error was a slight over-titration of NaOH during the back-titration
process, which could have led to slightly lower calculated moles of HCl neutralized, shown in
percent error. A new technique I learned was the back titration, which is useful when direct titration
isn’t practical due to reaction speed or solubility issues. A technique I could improve with more
practice is carefully performing the titrations with more patience, especially recognizing the
endpoint more precisely to reduce systematic error and improve accuracy of results. Overall, I think
this experiment was successful in determining the number of moles of acid neutralized per tablet
and the cost analysis per tablet.