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Antacid Lab

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Linda Qin

on 17 April 2014

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Transcript of Antacid Lab

Which antacid tablet is the best buy?
~one tablet of three different antacid brands
~0.2 M HCL [7.3g/L]
~0.1 M NaOH [4g/L]
~mortar and pestle
~electronic scale
~methyl pH color indicator
~graduated cylinder
~plastic containers
~Erlenmeyer flask
1. Ground tablets into dust (therefore able to be dissolved)
2. Weigh the dust then record data
3. Take a fifth of the weight of a tablet; put the rest into the small container.
4. Dissolve the fifth into 25mL of 0.2M HCl.
5. Take the initial reading of the 0.1M NaOH in the buret. Record.
6. Add two drops of the methyl orange indicator.
7. Slowly add in drops of NaOH to the HCl solution until the solution is tipping between orange and yellow.
8. Record the end reading of NaOH on the buret.
9. Repeat with the other two tablets.
10. Do three more trials.

1. precautions taken in this lab include wearing goggles at all times during trials
2. no running in the lab
3. caution taken to not spill substances on skin
4. being careful not to mix separate solutions
5. we wiped up our area afterward in case we spilled some powder and in case some drops of HCl/NaOH dripped from the burette
Percent Yield
[HCl Neutralization/gram]
Found by: moles of CaCO3 (or Mg[OH]2)/gram of tablet * 2
[1:2 ratio in chemical equation]

Full Chart
Conclusion Questions
1. Does Rolaid consume 47x its own weight in stomach acid?
According to our data, Rolaids consumes 100x its own weight in stomach acid, which is actually more than what the ad claimed.
2. Does Tums neutralize 1/3 more acid than Rolaids?
Rolaids: 0.01mol HCl/1g * 1.8g/tablet =
.018mol HCl/tablet
Tums: 0.00795mol HCl /1g * 2.0g/tablet=
.0159mol HCl/tablet
No, since Rolaids neutralizes more HCl per tablet than Tums.
Objective Questions
1. Which antacid neutralizes most the stomach acid?
The Experiment
The Data
Sources of Error
1. over underestimation of measurements
2. the weight scale could not display the weight to the thousandths place
3. measurements for using NaOH may be a bit inaccurate due to eyeballing the tick marks on the burette
4. during the dissolving process, the solution may have turned after a few too many drops
5. color is a subjective observation. the shades of color are too similar to absolutely differentiate and classify [especially since the color of the antacid tablet and drops of indicator changed the color output]
6. Rolaids did not dissolve entirely [perhaps some other materials were added into the tablet]

Average Moles
Rolaids-- 0.010 [0.01]
Tums-- 0.0080 [0.007950]
CVS-- 0.0074 [0.007365]
Moles of NaOH used: Volume [L] x 0.1
[Volume found by end titration—beginning]
...Moles of HCl used: Volume [L] x 0.2
Moles of HCl neutralized by tablet: initial HCl moles — NaOH moles used
-Chemical equations:

HCl + NaOH = H O + NaCl [1:1]

CaCO + 2HCl = CaCl + H CO [1:2]

Mg(OH) + 2HCl = MgCl + 2H O [1:2]
-Rolaids predicted: 0.010 mol HCl/gram
(0.0075mol by CaCO3 + 0.0026mol by Mg[OH]2)
-Tums predicted: 0.0075 mol HCl/gram
-CVS predicted: 0.0083 mol HCl/gram
Rolaids actual: 0.010mol HCl/gram
Tums actual: 0.0080mol HCl/gram
CVS actual: 0.0074mol HCl/gram
(Average Moles HCl Neutralized) / (1 Gram)
Rolaids- 0.01
Tums- 0.007950
CVS- 0.007365
Take Moles HCl neutralized/Gram
(Each trial)

Divide by 4 (for the 4 trials)
Example (Rolaids) :

(0.0253 + 0.00790 + 0.01087 + 0.00870 ) = 0.04
0.04 / 4 = 0.01
2. Which antacid cost less ?
Cost per gram
(Grams per bottle)
: Neutralizes 0.01mol HCl/1g
10g needed to neutralized 0.1mol

Stomach Acid
: 0.1 M = 0.1mol HCl/1L
1L=1000ml --> Thus, as density=1g/mL, 1000g stomach acid = 0.1mol HCl

Rolaids- 4.04 cents
Tums- 3.64 cents
CVS- 2.89 cents
Find the mass of 1 tablet

2. Multiply by number of tablets in bottle (to find mass of bottle)

3. Divide the price of each bottle the mass to find cost/gram
3. which antacid is the best buy ?
Best Buy: Cost/1 Mole of Stomach Acid Neutralized
Grams of tablet to neutralize 1 mole stomach acid:
Rolaids- 0.01mol/1g = 1mol/x -->
x = 100g
Tums- 0.007950mol/1g = 1mol/x -->
x = 125.8g
CVS- 0.007365mol/1g = 1mol/x -->
x = 135.8g
Cost for gram amount found above:
Rolaids- 100g * $0.0404/g --> $4.04
Tums- 125.8g * $0.0304/g --> $4.58
CVS- 135.8g * $0.0289/g --> $3.92
Sources Cited
"Determining the Effectiveness of an Antacid." Grossmont.edu. Grossmont College, n.d. Web. 16 Apr. 2014.
"Lab 4 - Determination of the Amount of Acid Neutralized by an Antacid Tablet Using Back Titration." Webassign.net. General Chemistry, 2011. Web. 16 Apr. 2014.
Hill, Logan. "Antacid Effectiveness Lab." Scribd.com. Scribd, 26 Oct. 2006. Web. 16 Apr. 2014.
Full transcript