Neutralise Excess Stomach Acid

Essay by Yourmumma April 2004

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Aim:

To find which powder, of four, is best for neutralising excess stomach acid.

Prediction:

With stomach pain relief powders being a consumer product, I predict that the best cure for neutralising a build up of stomach acid will be the one which has the lowest cost to successfully neutralise the dilute hydrochloric acid (HCl) (0.5 mol) (to represent the excess acid found in our stomachs). This powder would have be the one which costs less than any of the others to bring the acid build up to a neutral pH of 7. This is because it would make it more affordable and uses a low amount of powder at the same time. I will be measuring how much hydrochloric acid it takes to neutralise 25.0ml of remedy solution.

Stomach Powders:

The powders in question are used for curing acid indigestion. Heartburn and acid indigestion is discomfort in the upper digestive tract.

It can affect all ages but is common in adults over 60 years old. The symptoms could be mistaken for a heart attack or a heart attack could be mistaken for indigestion. Symptoms of this malady include: belching or slight regurgitation of stomach contents into the mouth, giving an acid taste, burning or uncomfortable feeling in the chest, difficulty swallowing, mild abdominal pain or bloating, and occasional nausea or vomiting. This unpleasant condition can be avoided by refraining from smoking, overindulging in food and, especially, alcohol. Other measures include decreasing fat in the diet, not wearing tight clothing, and trimming down if you are overweight. Neutralising the excess hydrochloric acid in the stomach can treat acid indigestion. Adding a base or a carbonate, producing water, which is not a problem, usually does this.

Aci - Go marketed by "Winterfields" and costs £1.80 for 100g. (£1.80 / 100g)

Ban - H+ made by "Waxo-Gelcome" has been subject of a nationwide television advertising campaign, and costs £1.25 for 50g. (£2.50 / 100g)

Contracid a popular "Wellington Pharmaceuticals" product, and costs £2.10 for 100g. (£2.10 / 100g)

Destracid made by "Fresco" and costs £3.50 for 200g. (£1.75 / 100g)

Having done a little research, I discovered that the indigestion remedies could be any of a few chemicals, here are the results:

Sodium Bicarbonate or Sodium Hydrogen Carbonate:

The most popular brands of medication that contain sodium carbonate are Alka-Seltzer and Brom-Seltzer. Alka-Seltzer has aspirin, which could be a stomach irritant. This reaction should take place:

NaHCO3 + HCl NaCl + H2O + CO2

Calcium Carbonate:

Calcium carbonate is a fast acting cure. The compound is a powder made from chalk, bones and shells. Like sodium based cures these compounds are good in small doses for short-term relief. Too much calcium can damage the kidney and lead to calcium deposits.

CaCO3 + HCl CaCl + H2O + CO2

Magnesium Hydroxide:

This forms magnesium chloride (a harmless salt) and water in the stomach to calm indigestion.

Mg(OH)2 + 2HCl MgCl2 + 2H2O

Indicators:

Choosing an indicator was another main task. Acid - Base indicators (also known as pH indicators) are substances which change colour with pH. They are usually weak acids or bases dissolved in water.

I had several different indicators to choose from, they are described below:

Universal Indicator:

A universal indicator is a solution which undergoes several color changes over a wide range of pH's. The colour is used to "indicate" pH directly. Universal indicators are usually mixtures of several indicators. A mixture of pH indicators, used to gauge the acidity or alkalinity of a solution. Each component changes colour at a different pH value, and so the indicator is capable of displaying a range of colours, according to the pH of the test solution, from red (at pH 1, strong acid) through green (neutral) to purple (at pH 13, strong alkali).

Bromothymol Blue:

Bromothymol blue changes from one colour to another as the pH of the solution it is in is altered. Bromothymol blue is yellow in acidic solutions and blue in basic solutions.

Methyl Orange: C14H14N3NaO3S

Chemists use methyl orange as an indicator in the titration of weak bases with strong acids. It changes from red (at pH 3.1) to orange-yellow (at pH 4.4).

Litmus:

Litmus is a substance that is commonly used in chemistry to indicate whether a solution is an acid or a base. It comes in an acidic form, which is red, and a basic form, which is blue. An acidic solution will turn blue litmus red, but will not affect red litmus. A basic solution will turn red litmus blue, but will not affect blue litmus. A neutral solution, which is neither acidic nor basic, will not change the color of either litmus.

Litmus may be dissolved in water or alcohol to make an indicating solution. Because litmus is an intensely colored substance, only a few drops of litmus indicator need to be added to a solution to tell whether it is acidic or basic.

I decided that litmus would be the best indicator solution to use for my experiment. At first I thought that universal indicator would be best, because of its wide range of colours, each one indicating a different pH level. However, the universal indicator given to us did not function properly, so was discarded. I chose against methyl orange for the reason that, as you can see below, the range of pH levels is not very broad, so was also discarded. This was also the reason for choosing against the bromothymol blue. Although litmus doesn't have a huge range of indicated pH levels, there were more than the others. The chart below shows other indicators. I would not have chosen them because they concentrated on different pH levels of alkali solutions, and therefore would not have been chosen either.

Source:

http://www.ask.com/main/metaanswer.asp?metaEngine=directhit&origin=0&MetaURL=http%3A%2F%2Fask%2Edirecthit%2Ecom%2Ffcgi%2Dbin%2FRedirURL%2Efcg%3Furl%3Dhttp%3A%2F%2Fwww%2Ecarlton%2Epaschools%2Epa%2Esk%2Eca%2Fchemical%2Fequilibrium%2Fabindicators%2Ehtm%26qry%3D%2522acid%2B%252D%2Bbase%2Bindicator%2522%26rnk%3D1%26src%3DDH%5FAsk%5FSRCH&qCategory=jeeves&metaTopic=Acid+Base+Indicators&ItemOrdinal=0&logQID=88364ADBF7BB4D48A77D8CF4165EDC7B&sv=2000&back=http%3A%2F%2F

Apparatus:

Burette Used to drip HCl (stomach acid) accurately into mixture of water and remedy powder. A burette was used because it is extremely accurate and can hold up to 50ml of liquid, and is accurate to a tenth of a millilitre for example 25.0ml. This was cleaned to avoid contaminating the hydrochloric acid.

100ml beaker Used to contain mixture of chemicals (water, powder, then HCl also). It was used to mix the chemicals together. Used instead of conical flask because it has larger opening therefore making it easier to drip HCl from burette into and it is also smaller. All were cleaned before the experiment began to avoid contaminating the solution. This could have given me anomalous results.

Clamp To hold burette steady above beaker.

Water To mix with the stomach remedies to allow a clearer pH reading. I needed water which was as close to pH seven as possible to ensure that it would affect the results as little as possible. At first, I tried to use distilled water, but discovered it was very acid, so resorted to tap water, which was near on neutral.

Top-pan balance To accurately measure out the mass of stomach powder needed accurately. This can be done to within one hundredth of a gram, for example: 25.00g.

Litmus Indicator This was chosen over other indicators to progressively show the acidity of the solution. We chose this over other indicators, such as universal indicator, methyl orange and bromothymol blue because we found it easier to tell when a substance was neutral, acid, or alkali. The universal indicator did not function as it should (have a wide range of colours indicating pH levels) therefore it was not chosen, as we wanted to be as accurate as possible. We used litmus indicator in its base form (we can tell this because it was a deep blue, the acid form is red) because acid based indicators only change from one colour to another, instead of having a range.

Stirring Rods Used to stir the solution. They had to be cleaned before use to be sure that the solution was not contaminated.

Measuring Cylinder Used to measure water accurately. It had to be cleaned beforehand to avoid contamination of any sort which could drastically change the results.

Stomach Powders Used to neutralise the diluted HCl (stomach acid).

Funnel This was used to help with filling the burette with HCl. I ensured that it was as clean as possible to avoid any contamination.

Hydrochloric Acid (HCl) This was used to represent stomach acid, as it is a lot more practical to use than the real thing! The concentration of HCl was 0.5 mol per litre of water.

Spatula This was used to put the stomach remedies into the beakers. It was very important that we washed them beforehand to avoid any contamination of any sort as this would risk anomalous results.

Stomach Remedies (see above)

Variables:

Throughout the entire experiment, I must ensure that certain variables are kept precisely the same. These are called the controlled variables. They are necessary to be sure that the experiment is 100% fair and as accurate as possible throughout the result taking sessions. Any controlled variables that are modified could lead to rogue results, and this result would prove that something was not going as planned.

Controlled Variables:

Mass of Indigestion Remedy:

This must be kept the same throughout the experiment, for each powder. I checking that the mass of the powder is accurate to the exact 100th of a gram will ensure this. This is important because if any more or any less of the remedy is used, it will change the amount of HCl needed to neutralise it.

Volume of Water:

I will use 25.00ml of water throughout the entire experiment. Like above, if the amount of water is changed in the middle of the experiment, it will change the amount of HCl needed to neutralise the solution.

Concentration of HCl

This is important, because I need to have the concentration as close to that of real stomach acid as possible. 0.5 mol is available to me. This is close enough. If the concentration was any higher, it would take a smaller amount to neutralise the solution, and if there was a lower concentration, then it would take more.

Room Temperature

This is important because if the room temperature was much higher or lower in one session than in another, the experiment would have been greatly affected. This is because a higher temperature would increase the energy that the particles of any of the chemicals would have more energy than on another day. This is one reason why I tried to do all the experiment during one one hour session.

Uncontrolled Variable:

I have chosen to only measure for one uncontrolled variable. The main reason for this is to have time, and it is far simpler. This variable is:

Volume of HCl added to the solution

I used this as the uncontrolled variable instead of the amount of solution added to the HCl because it is a lot easier to control and measure. Had I done the other way round, then I would have constantly needed to clean a lot of my equipment before and after each test. It is also easier to calculate the results this way round.

Method:

The apparatus was set up as shown in the diagram below. I accurately measured out 2.00g of stomach remedy powder in clean 100ml beakers using the top-pan balance. The beakers needed to be as clean as possible to avoid contamination of the solution. I did this for all four of the given remedies, twice for each so that I could identify anomalous results if there were any. Then I added 25.0ml of water to each. I did this using a measuring cylinder because I wanted to be as accurate as possible, ensuring that I was not under or over 25.0ml. I did this because I discovered that many people prefer to take their medicine with water, as they find pills hard to swallow by themselves. Another key reason is that we found it easier to take a pH reading with water than without. The solute and the solvent were mixed together to form one solution. This was to ensure that when litmus indicator was added, we got a reading of the solution, not just the water. When I added two semi-filled pipettes litmus indicator to the solution, we observed the colour the solution became after a further stirring, and noted it down. I filled the burette with exactly 50.0ml of hydrochloric acid using a funnel to avoid any spillage. It needed to be filled exactly to 50.0ml, to get an accurate reading. I placed the beaker under the burette and carefully let HCl drip into the solution. I continued to do this in 1ml stages until the solution turned pinky red, to indicate neutrality of the solution. This was repeated twice for each of the remedies. The results were noted in a table.

Before I started to do the real experiment, I decided that it would be wise to do a preliminary experiment to check that my original parameters were acceptable. Theses are shown in the "variables" section below, along with the actual settings. During this primary period of experimentation, I ran numerous test to find out how much water or indigestion remedies to use. At first, my group and I thought that we should use around 100.0ml of water, but we found that it was too much because it took longer to get results. We also tried 50.0ml, but with similar consequences. We slipped down the other end of the scale, and experimented with 5ml and 10.0ml of water, but agreed that this was too little, and that the remedies were not being completely dissolved with so little water. I eventually discovered that 25.0ml was the right amount. I also had to decide on the amount of indigestion remedy to use. At first, I was confident that this figure would be around 8g - 10.00g, but was a little overwhelmed to discover that this was much too much. A large proportion of the powder was not being dissolved, even with vigorous stirring and mixing! I decreased the amount of powder until I was happy with a figure of 2.00g. I was surprised at how little I needed. However, it was just enough to be fully dissolved in the 25.0ml water. It was finding the right proportions of the constituents that was the key to success, and I was pleased to find that 2.00g of powder was just right for 25.0ml water.

Diagram:

Results:

All results are stated using 2.00g of powder, and 25.0ml of water to form a solution.

The different tests indicate each time that the experiment was carried out.

The numbers represent the amount of HCl required to neutralise the solution to make it pinky-red.

Volume of Acid Added (ml)

Remedy Test 1 Test 2 Test 3 (if required)

Destracid 15.2 15.1

Aci - Go 11.8 13.3 13.1

Ban - H+ 24.6 24.6

Contracid 30.9 30.8

I repeated the experiment for Aci - Go three times. I did it a third time because as you can see, the first two did not match up. This could be because we were careless when preparing the equipment, however, looking at the other results, it appears as though it was a one-off.

I calculated these results using the ones above, showing what would have happened using 25 times less remedy solution; 1.0ml water 0.08g remedy powder. The results show how much HCl would be needed to neutralise this.

Volume of Acid Added (ml)

Remedy Test 1 Test 2 Test 3 (if required) Average

Destracid 0.60 0.60 0.60

Aci - Go 0.44* 0.51 0.52 0.515

Ban - H+ 0.96 0.95 0.955

Contracid 1.20 1.20 1.20

*This result was omitted from calculating the averages, because it is obviously an anomalous result.

From the results, I could calculate the cost per gram for how much remedy was required to neutralise 1ml of HCl.

Remedy Amount to neutralise 1.00ml HCl (ml) amount of powder (g) cost to cure (p)

Destracid 1.60 0.13 0.234

Aci - Go 1.92 0.15 0.375

Ban - H+ 1.04 0.08 0.168

Contracid 0.83 0.06 0.105

The cost to cure column represents how much it would cost, (in pence) to neutralise 1ml of HCl.

Conclusion:

Looking back at my prediction and results, I conclude that Contracid is the best remedy for indigestion. I think this because as you can see above, it costs the least to neutralise 1.00ml of HCl. This is the order in which they are classified according to my results, they range from best to worst:

Contracid 0.105p to neutralise 1.00ml of excess HCl

Ban - H+ 0.168p to neutralise 1.00ml of excess HCl

Destracid 0.234p to neutralise 1.00ml of excess HCl

Aci - Go 0.375p to neutralise 1.00ml of excess HCl

From my results, I can tell that the powders are made of baking soda, or, Sodium Hydrogen Carbonate to be more accurate. I think this because all the reactions were very similar, and the powder itself had exactly the same texture, colour and consistency as baking soda at home. However, I suspect that chemicals were used to pad the baking soda out because usually, baking soda is very reactive, and during the experiment, it took more time to notice a big difference in the solution. Baking powder is also soluble, and the powder used to create the solutions dissolved. If none of the remedies were padded out, then the results would all have been the same. Padding chemicals are used to make pills and tablets bigger, but are almost unreactive, and do not affect the sodium hydrogen carbonate in any way. This is the reaction which will have taken place:

NaHCO3 + HCl NaCl + H2O + CO2

Evaluation:

I believe that my results were almost as accurate as I could get them, and I was pleased to see that the prediction and the conclusion matched. However, there are several things that I would want to change, had I the chance to repeat the experiment. Firstly, I would be more careful in the manner in which I measured results and the way I prepared the experiment. As you can see, there is one rogue result which was almost certainly a product of not accurately measuring the quantities of various chemicals or the fact that I may not have accurately observed readings when a test was carried out. The next time, I shall ensure that each test is repeated up to 5 times, to be sure of spotting anomalous results, and getting as accurate as possible as I felt that it was obvious from my results that two was not enough

However, many things went right throughout my experiment, I was relieved that the results matched up and were very consistent, except for one obvious rogue, and that my conclusion matches what I said in my prediction.

To improve the entire experiment, I would make sure that all the tests were carried out during one lesson, as it would ensure that all the chemicals were always identical. It may have been that the rogue result came from using HCl from a different bottle. However, to wrap things up, I am pleased to say that I believe that the experiment was a success.