A STUDY OF DISSOLVING ALKA-SELTZER IN DIFFERENT LIQUIDS
Enoch Kuan
Cary Academy
2012
ABSTRACT
The purpose of this experiment was to test the dissolving times of Alka-Seltzer tablets in different liquids. Alka-Seltzer tablets are little round antacid tablets that are made of sodium bicarbonate, potassium bicarbonate, and citric acid. An Alka-Seltzer tablet was dropped into 100 mL of water and at the same time, a timer was started. After the Alka-
Seltzer tablet dissolved completely, the time was taken and recorded. The Alka-Seltzer tablet was dissolved in three different liquids Sprite, water, or vinegar; the results showed that the Alka-Seltzer tablet dissolved the fastest in water and the slowest in
Sprite. The Alka-Seltzer tablet dissolved the quickest in the water because water is the liquid that the Alka-Seltzer tablet was designed to dissolve in. Also, Alka-Seltzer tablets dissolve quicker in larger amounts of liquid compared to smaller amounts of liquid.
INTRODUCTION
A long time ago, Sumerians used an antacid to relieve stomach aches. Excess stomach acids cause stomach aches. Antacids neutralize the excess acid so it can help settle stomach aches. Sodium bicarbonate is just baking soda, and to this day, a lot of stomach reliefs are just baking soda mixed with water. Sodium bicarbonate is a gentle salt that interacts with the hydrochloric acids in the stomach. In 1931, a new type of
Antacid compound called Alka-Seltzer was produced. Alka-Seltzer helps to cures indigestion, headaches and other pains. One tablet of Alka-Seltzer is mainly made of
1.0g of sodium bicarbonate, 0.3g of potassium bicarbonate, and 0.8g of citric acid.
These three substances cause a reaction in water that leads to carbon dioxide release.
If there is a homogeneous mixture or a mixture that is uniform throughout, it is in most cases, a solution. A solution is a minor component, solute, dissolved into a major
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component which is a solvent. For example, salt is mixed into water, the salt dissolves into water, but the water doesn’t change, except for the fact that there is now salt in it.
That is exactly what dissolving is. It is adding and mixing into the base substance, but not altering it. When a solute dissolves into a solvent, the solute disappears because the solute has become part of the solution; in other words, the particles of the solute are now mixed with the particles of the base substance. Alka-Seltzer tablets dissolve in water. When an Alka-Seltzer tablet is dropped in water, the sodium bicarbonate, potassium bicarbonate, and the citric acid dissolve to produce carbon dioxide. This happens by the sodium bicarbonate and the citric acid of the tablet reacting in the water to carbonic acid. As the concentration of carbonic acid increases, it decomposes to make carbon dioxide and water.
Polar and non-polar are two terms that are basically the same as hydrophilic and hydrophobic, respectively. A polar molecule is referring to whether or not the molecule is charged. When a molecule is non-polar, that means that it doesn’t have any charge at all. For example, in a water molecule, there is an oxygen atom and two hydrogen atoms. The oxygen atom attracts more electrons than the hydrogen atoms. Since electrons are negatively charged, the hydrogen atoms end up being positively charged and the oxygen atom ends up being negatively charged. When there are two water molecules together, the hydrogen atoms attract to the oxygen atom because negatively charged atoms attract to positively charged atoms. There are also molecules that don’t have any charge, such as an oil molecule. Oil molecules, or anything that has no charge, attract to each other. That is also why oil and water don’t mix. When water, which is negatively and positively charged, and oil, which has no charge at all, are in the same container, the water molecules find each other and the oil molecules find each other, but neither molecule will attract to the other because there are other molecules that have strong attraction to it.
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Figure 1: How polarity affects the interaction between oil and water.
A mixture where the composition is uniform is homogeneous. All the parts of a homogeneous mixture are the same; they have the same properties and composition.
One example of homogeneous mixtures is air. The main idea of a homogeneous mixture is that the composition is the mixture is evenly spread out. A heterogeneous mixture where the ingredients can be easily identified, when there are two or more ingredients present. Two examples of a heterogeneous mixture are pizza and a chocolate chip cookie. For chocolate chip cookies, the dough and the chocolate chips can be seen separately, there for is heterogeneous. Salt is one of many substances that can dissolve in water to make a homogeneous mixture. If something is mixed into a homogeneous mixture that means that the substance
’s particles, mix in with the particles of the base substance. That forms a substance that is uniform in texture, color, and thickness.
Solids, liquids, and gases are made of atoms, particles, and/or ions. Microscopically, gases are irregular. Their particles are separated a lot from each other and are in no arrangement or order. The particles vibrate and move at high speeds. Gases will take
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the shape of the container they are in. Gases are also easily compressible because there is a lot of free space in between the particles. In liquids, their particles are close together, but they’re still not in any arrangement and they slide around each other.
Liquids will fill part of the contain they are in. Liquids are not easily compressed because there is little space between the particles. The particles in solids are packed together and are in a pattern. The particles vibrate, but don’t move. Solids are ridged and are in a fixed shape and volume. Solids are definitely not easily compressible because of the lack of space in between the particles.
Collin Dworsky did an experiment testing the dissolving times of different types of
Ibuprofen. The Ibuprofen was put in 250 mL of water and timed until it was completely dissolved. He found that Good Sense Ibuprofen dissolved the fastest regardless of the solution it was in because it always broke up in to small pieces which let liquids get in between the particles of the solution that then made dissolving easier because more sides of the tablet are exposed to the liquid.
MATERIALS & METHODS
Beakers, water, Sprite, stopwatch, White Distilled Vinegar, pH probe, and Alka-Seltzer tablets were used in this experiment.
An Alka-Seltzer tablet was dropped into a beaker with 100 mL of water in it. At the same time, a stopwatch was started and it timed how long it took for the Alka-Seltzer tablet to dissolve. After the Alka-Seltzer dissolved, the time was recorded. This experiment was repeated three times. The same experiment was also completed with distilled white vinegar and then Sprite.
The procedure above was repeated but instead of using one Alka-Seltzer tablet for each trial, two were used.
The initial experiment was repeated but instead of dropping the Alka-Seltzer tablet in three types of liquid, only water was used. In addition to that, the Alka-Seltzer tablet was dropped in 100 mL, 300 mL, and 500 mL of water instead of just 100 mL of water.
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120
100
80
60
40
20
0
25 mL, 50 mL, and 100 mL of Sprite were put in separate containers and their pH was measured. Then, an Alka-Seltzer tablet was dropped in. After the Alka-Seltzer Tablet dissolved, a pH probe was put in the sprite for 30 sec to measure its pH.
Five Alka-Seltzer tablets were put in a beaker with 100 mL of water. At the same time, a stop watch was started to measure the time it took the Alka-Seltzer tablets to dissolve.
The experiments were repeated with 200 mL, then 300 mL of water.
RESULTS AND DISSCUSSION
In this experiment, the Alka-Seltzer tablet dissolved the fastest in water and the slowest in Sprite (Figure 2). In water, the Alka-Seltzer tablet could consistently dissolve the fastest, 62 sec, compared to dissolving in Sprite, 97 sec, or Vinegar, 83 sec. The Alka-
Seltzer dissolved the slowest in Sprite. This happened because the Alka-Seltzer tablet was designed to dissolve in water; therefore, it worked the best in water. The Alka-
Seltzer tablet is an antacid; so it’s designed to neutralize acids. In Sprite, there is citric acid. So, what happens is the Alka-Seltzer tablet takes long to dissolve because there is more acid to neutralize. Also, there is already carbon dioxide in Sprite and Alka-
Seltzer tablets produce carbon dioxide, so that variable slows down the process as well.
Spirte Water
Type of liquid
Vinegar
Figure 2: The dissolving times of Alka-Seltzer tablets in water, Sprite and Vinegar.
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In this experiment, the two Alka-Seltzer tablets were dissolved in 100 mL of water,
Sprite and White Distilled Vinegar. The two Alka-Seltzer tablets dissolved in about the same time as one tablet did in water, 64 sec, Sprite, 100 sec, and vinegar, 90 sec
(Figure 3). It was hypothesized that the two Alka-Seltzer tablets would dissolve faster than one Alka-Seltzer tablet. The reason behind this hypothesis was that Alka-Seltzer tablets produce carbon dioxide due to the decomposition of carbonic acid. If the carbonic acid concentration doubled in the same amount of liquid, the dissolving time would go down. What happened was that the dissolving times stayed at about the same with some variety.
120
100
80
60
40
20
0
Sprite Water
Type of Liquid
Vinegar
Figure 3: The dissolving times of two Alka-Seltzer tablets in water, Sprite, and vinegar.
In this experiment, one Alka-Seltzer tablet was dissolved in 100 mL, 300 mL, and 500 mL of water. The Alka-Seltzer tablet dissolved the fastest in the 500 mL of water
(Figure 4). This happened because the Alka-Seltzer tablets release carbon dioxide into the water, if there is more water, then there is more liquid to release carbon dioxide into, therefore, decreasing the dissolving time of the Alka-Seltzer tablets.
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70
60
50
40
30
20
10
0
0 100 200 300 400
Amount of Water (mL)
500 600
Figure 4: The dissolving times of five Alka-Seltzer tablets in 100 mL, 300 mL, and 500 mL of water.
In this experiment, five Alka-Seltzer tablets were dissolved in 100 mL, 200 mL, and 300 mL, of Sprite. The Alka-Seltzer tablet dissolved the fastest in 300 mL of water, 42 sec
(Figure 5). In experiment three (Figure 4), the Alka-Seltzer tablet also dissolved the quickest in the largest amount of water. The Alka-Seltzer tablet(s) dissolve the fastest in larger amounts of liquid because in a small container with liquid, the Alka-Seltzer tablet releases lots of carbon-dioxide, but at one point, the Alka-Seltzer tablet slows down in dissolving because the liquid has reached its capacity in carbon-dioxide. In a larger amount of liquid, that capacity is great than that of the little amount of liquid.
80
70
60
50
40
30
20
10
0
0 50 100 150 200
Amount of Liquid
250 300 350
Figure 5: The dissolving times of an Alka-Seltzer tablet in 100 mL, 200 mL, and 300 mL of Sprite.
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In this experiment, the pH of 25 mL, 50 mL, and 100 mL of Sprite were measured.
Then, an Alka-Seltzer tablet was dropped in. After the Alka-Seltzer tablet dissolved, the pH of the Sprite was measured again. Since the Alka-Seltzer tablet is an Antacid, it is supposed to neutralize acid. In Sprite, there is citric acid. What is expected to happen is the pH of the Sprite is supposed to go more basic, which is higher digits on the pH scale. The results showed no trend in the change of pH. The lowest change of pH was the 400 mL of Sprite (Figure 6). This was expected because there was the most citric acid in higher amounts of liquid. Therefore, it is harder for the Alka-Seltzer tablet to neutralize all the acid.
3.5
3
2.5
2
1.5
1
0.5
0
0 100 200 300
Amount of Liquid (mL)
400 500
Figure 6: The average pH changes of Sprite (Before/After Alka-Seltzer.
CONCLUSION
The Alka-Seltzer ended up dissolving the fastest in water. In addition to this, Alka-
Seltzer tablets dissolve quicker in larger amounts of water. This data is important b ecause it shows that higher concentrations of carbonic acid don’t necessarily cause the dissolving time of an Alka-Seltzer to drop. The hypothesis was correct because the
Alka-Seltzer tablet dissolved the fastest in water. To follow up this experiment, Alka-
Seltzer tablets could be dissolved in different liquids with varying pH’s.
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CITATIONS
“Antacid.” Encyclopedia Britannica. Encyclopedia Britannica Online School Edition.
Encyclopedia Britannica, Inc., 2012. Web. 20 Jan. 2012.
“Gases, Liquids, Solids.”
Purdue University Department of Chemistry . Purdue
University. Feb. 15, 2012. Web. Feb. 15, 2012. http://www.chem.purdue.edu/gchelp/liquids/character.html
Merryann12. “Heterogeneous and Homogeneous Mixtures.” Hubpages. Feb. 15, 2012.
Web. Feb. 15, 2012
Patrick , Bethanne and John Thompson. An Uncommon History of Common Things.
Washington D.C.: National Geographic. 2009. Print.
Snyder, Carl H. The Extraordinary Chemistry of Ordinary Things.
New York: John Wiley
& Sons, Inc. 1998. Print
Wikipedia contributors. "Mixture." Wikipedia, The Free Encyclopedia . Wikipedia, The
Free Encyclopedia, 7 Feb. 2012. Web. Feb. 15, 2012
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