Ca CO3(s) + 2 HCl (aq) → Ca Cl2 (aq) + CO2 (g) + H2O (l)
Magnesium carbonate (s) + Hydrochloric acid (aq) → Magnesium Chloride (aq) + Carbon Dioxide (g) + Water (l)
Mg CO3(s) + 2 HCl (aq) → Mg Cl2 (aq) + CO2 (g) + H2O (l)
Sodium bicarbonate (s) + Hydrochloric acid (aq) → Sodium chloride (aq) + Carbon Dioxide (g) + Water (l)
NaHCO3 (sol)+ 1HCl (aq )→ 1Na Cl (aq)+ H2O (aq) + CO2 (gas)
Initial Calculations.
For all these calculations I shall be using 1 Molar of hydrochloric acid.
Moles of antacid acid = mass / relative formula mass
Number of moles of acid needed to neutralise antacid tablet:
= 2 x number of moles of the antacid chemical.
Predicted volume of acid needed to neutralise the antacid:
= Moles of acid
----------------------- = predicted volume in dm3
Concentration of acid
To change dm3 into cm3 you times it by 100.
Calculations for Settlers, Superdrug and Rennie rap- eze .
Moles of antacid= 500 mg (0.5g) divided by 100 (RFM) = 0.005 moles
Number of moles= 2 x 0.005 moles = 0.010 moles of acid needed to neutralise the antacid tablet.
Predicted volume of acid = 0.01 moles divided by 1= 0.01 dm cubed
0.01 x 1000 = 10 cm cubed to neutralise the antacid.
Calculations for Rennie (pepper mint flavour) antacid tablet.
Note: This tablet is different to the ones above it has an extra carbonate ingredient so it will be different.
Number of moles in each chemical in Rennie (pepper mint flavour):
For Calcium carbonate.
Moles of antacid = 680 mg (0.68g) divided by 100 (RFM) = 0.0068 moles
Number of moles of acid = 2 x (0.0068 moles) = 0.0136 moles of acid .
Predicted volume of acid =0.0136 moles divided by 1= 0.0136 m cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal = 13.6 cm cubed to neutralise the antacid.
For Magnesium carbonate.
Number of moles = 80 mg (0.08g) divided by 84 (RFM) = 0.001 moles
Moles of the acid= 2 x 0.001 moles = 0.002moles of acid needed to neutralise the antacid tablet.
Predicted volume of acid needed to neutralise the antacid:= 0.002 moles divided by 1= 0.002dm cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal = 0.2 cm cubed to neutralise the antacid.
Predicted volume= 0.2 cm cubed + 13.6 cm cubed = 13.8 cm cubed of acid needed to neutralise the tablet
Calculations for Boots antacid tablet.
Note: This tablet is different to the ones above but it has the same ingredients as boots antacid tablet.
For Calcium carbonate.
Number of moles of antacid= 200 mg (0.2g) divided by 100 (RFM) = 0.002 moles
Number of moles of acid = 2 x 0.002 moles = 0.004 moles of acid needed to neutralise the antacid tablet.
Predicted volume of acid needed to neutralise the antacid= 0.004 moles / 1= this will equal 0.004 dm cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal = 4 cm cubed of HCl to neutralise the antacid.
For Magnesium carbonate.
Number of moles = 600 mg (0.06g) divided by 84 (RFM) = 0.0007 moles
Number of moles of acid = 2 x 0.0007 moles = 0.0014 moles of acid
Predicted volume of acid needed to neutralise the antacid:
= 0.0014 moles divided by 1= this will equal 0.0014dm cubed
So you shall times this by 1000 to get it in cm cubed = 1.4 cm cubed to neutralise the antacid.
For Sodium Bicarbonate.
This number will be two because the reaction is:
NaHCO3 (sol)+ 1HCl (aq )→ 1Na Cl (aq)+ H2O (aq) + CO2 (gas)
There is a 1 :1 reaction there are 1 hydrochloric acids to react with 1 magnesium carbonate.
= 1 x 0.0007 moles = 0.0007 moles of acid needed to neutralise the antacid tablet.
Predicted volume of acid = 0.0007 moles divided by 1= this will equal 0.0007 dm cubed
So you shall times this by 1000 to get it in cm cubed 0.7 cm cubed to neutralise the antacid.
The amount of acid to neutralise the antacid shall equal the amount it took to neutralise the calcium carbonate plus the amount it took to neutralise the magnesium carbonate and sodium bicarbonate:
4 + 1.4 + 0.7 = 6.1 cm cubed of acid needed to neutralise the tablet.
Calculations for Bisodol antacid tablet.
Note: This tablet is different to the ones above it has 2 extra carbonate ingredients so it will be different.
Number of moles in each chemical in Boots antacid tablet:
For Calcium carbonate.
Number of moles = 522 mg (0.522g) divided by 100 (RFM) = 0.00522 moles
Number of moles of acid = 2 x 0.00522 moles = 0.01044 moles of acid
Predicted volume of acid needed to neutralise the antacid:
= 0.01044 moles divided by 1= this will equal 0.01044 dm cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal =10.4 4 cm cubed of HCl to neutralise the antacid.
For Magnesium carbonate.
Number of moles = 68 mg (0.068g) divided by 84 (RFM) = 0.00081 moles
Number of moles of acid = 2 x .00081 moles = 0.0016 moles of acid
Predicted volume of acid = 0.0016 moles divided by 1= this will equal 0.0016dm cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal = 1.6 cm cubed to neutralise the antacid.
For Sodium Bicarbonate.
Number of moles = 64 mg (0.064g) divided by 84 (RFM) = 0.00076 moles
Number of moles of acid=1 x 0.00076 moles = 0.00076 moles of acid
This number will be one because the reaction is:
NaHCO3 (sol)+ 1HCl (aq )→ 1Na Cl (aq)+ H2O (aq) + CO2 (gas)
There is a 1 :1 reaction there are 1 hydrochloric acids to react with 1 sodium bicarbonate.
Predicted volume of acid =0.00076 moles / 1= this will equal 0.00076 dm cubed
So you shall times this by 1000 to get it in cm cubed so it shall equal = 0.76 cm cubed to neutralise the antacid.
The amount of acid to neutralise the antacid =10.44 + 1.6 + 0.76 = 12.8 cm cubed of acid needed to neutralise the tablet.
Experiment.
Preliminary experiment.
Equipment needed:
- 50 ml Burette
- A bottle of Hydrochloric acid ( 1 molar)
- A bottle of the indicator Bromophenol blue
- Funnel
- Beaker
- Conical flask
- Goggles
- Pestle and Mortar
- White tile
- Clamp Stand
- Balance
- Spatula
- Measuring cylinder.
- Petri dish
- The following antacid tablets:
- Settlers
- Superdrug
- Rennie (pepper mint flavour)
- Rennie Rap-eze (fruit flavour)
- Boots
- Bisodol
First Plan.
Set up the equipment as shown in the diagram on the next page:
Crush 3 settlers antacid tablet using a pestle and mortar. We are doing this because it will increase the surface area of the tablet so more of it is able to react with the acid.
Put the Petri dish on the balance and then reset the scales.
Then weigh out 0.5g of the crushed tablet. We are doing this to make sure that this is a fair test and there is the same amount of antacid tablet for each tablet.
Put this into the empty conical flask.
Fill the burette up to the 0 marker reading from the bottom of the meniscus. Again we are reading from the bottom of the meniscus to make sure it is a fair test.
Fill the burette by connecting it to the clamp stand and put it underneath eyelevel. It is essential that goggles are worn at this point. You would put it under eye level by putting it on a stool, put the funnel into the burette then pour the 1 molar HCl from the beaker into the burette. We are putting it onto a stool so no acid will enter the eye and the goggles are used for the same reason.
Then measure out the 20ml of water and put into conical flask. Then add a few drops of Bromophenol blue. I am using Bromophenol blue because when it is alkaline it is a very distinctive purple and when it is an acid it is a bright yellow so there fore it will be easy to see the change in colour.
Then open the tap and let out 0.5 ml of acid out and shake do this again until it does not turn back to purple. We are letting out only 0.5 ml out because it will make the results more accurate.
Take down the results showing the difference.
Repeat this process again for every other antacid tablet and take down the result.
When starting the next tablet you do not have to fill the burette up to 0 but take a note of where it was then calculate the difference.
We shall only be doing this once because it is a preliminary experiment.
Results.
Analysing results.
I found that my results were not very accurate this may have been because I did not transfer the entire 0.5g of the crushed tablet from the Petri dish into the water so therefore different amounts will be taken in by different tablets. Also the way I let 0.5 out each time would not have give out good results because the acid may have neutralised between each 0.5 of a millilitre. It also was not accurate because when the results are being read they are not exact they would not be exact because it will be very hard to read the burette accurately using the naked eye, although this would have not made a large change. Another thing on why it was not accurate is that we could not exactly measure 0.5g so therefore there was a change in mass of each antacid tablet. I think another thing that did not make it accurate is that 20ml of water was not enough because the tablet did not dissolve easily enough. But we did find it accurate in some ways because it was very clear in the change of colour between the purple and yellow.
At this point I am not sure which tablet is the best especially with the results I have received because it is still very close between Bisodol and Rennie.
Prediction
Now that I have done my preliminary experiment and I have done my initial calculations I will predict that Rennie will be the most effective because it has been proven in the initial calculations and in my preliminary results although it may be close between Bisodol and Rennie (peppermint flavour). Also I think the worst tablet well definitely be the Boots antacid tablet but I think third place will be very close but in theory they should all get the same results.
Extra equipment needed.
- Stirring rod
- Magnetic stirrer
- Small brush
Solutions
To conquer the above problems I shall do the following:
Brush out the reminder of crushed tablet into the water.
Instead of letting out 0.5 ml of HCl each time I shall let out 0.2 to make the experiment even more accurate.
Spend more time reading the results.
Spend more time weighing the tablets.
Add 5 ml more of water
Adapted plan
Note: some parts may be the same as the preliminary plan.
Crush 3 settlers antacid tablet using a pestle and mortar. We are doing this because it will increase the surface area of the tablet so more of it is able to react with the acid.
Put the Petri dish on the balance and then reset the scales.
Then weigh out 0.5g of the crushed tablet. We are doing this to make sure that this is a fair test and there is the same amount of antacid tablet for each tablet.
Put this into the empty conical flask using a brush to get the excess crushed tablet in and make sure the magnetic stirrer is in the conical flask and make sure that the conical flask is very clean.
Fill the burette up to the 0 marker reading from the bottom of the meniscus. Again we are reading from the bottom of the meniscus to make sure it is a fair test.
Fill the burette by connecting it to the clamp stand and put it underneath eyelevel. It is essential that goggles are worn at this point. You would put it under eye level by putting it on a stool, put the funnel into the burette then pour the 1 molar HCl from the beaker into the burette. We are putting it onto a stool so no acid will enter the eye and the goggles are used for the same reason.
Then measure out the 25ml of water and put into conical flask and use the stirring rod to mix the solution.
Then add a few drops of Bromophenol blue. I am using Bromophenol blue because when it is alkaline it is a very distinctive purple and when it is an acid it is a bright yellow so there fore it will be easy to see the change in colour.
Then open the tap and let out 0.2 ml of acid out and turn on the magnetic stirrer to mix this and do this again until it does not turn back to purple. We are letting out only 0.2 ml out because it will make the results more accurate.
Take down the results showing the difference.
Repeat this another 2 times.
Then repeat this process again for every other antacid tablet and take down the result.
When starting the next tablet you do not have to fill the burette up to 0 but take a note of where it was then calculate the difference.
Saftey.
Make sure all times when this experiment is being conducted that goggles are being worn. This is to protect eyes from any strong acids getting in them.
Also make sure the test is being conducted under eyelevel this is mainly because the reason above.
Another issue of safety is that it is very important to be careful when pouring the HCl if it does get on you or a piece of clothing then thoroughly wash out with water.
Fair test.
To make this a fair test I have decided to weigh out the crushed tablet so each test will get the same amount of antacid tablet. I have also increased the fairness by brushing off extra bits of crushed tablet into the conical flask. Also I shall spend longer on observing like when reading the mark on the burette. I shall also spend more time weighing out the crushed tablet so I can get as close to 0.5 as I am able to.
Results.
Average results.
How many moles of acid it took to neutralise the tablet using the average results.
Settlers
9.2 divided by 1000 = 0.0092cm3
Moles of HCl = concentration x volume = 1 x 0.0092cm3 = 0.0092 moles needed to neutralise the acid.
Superdrug
9.6 divided by 1000 = 0.0096cm3
Moles of HCl = concentration x volume = 1 x 0.0096cm3 = 0.0096 moles needed to neutralise the acid
Rennie
13.8 divided by 1000 = 0.0138cm3
Moles of HCl = concentration x volume = 1 x 0.0138cm3 = 0.0138 moles needed to neutralise the acid
Rennie rap-eze.
9.8 divided by 1000 = 0.0098cm3
Moles of HCl = concentration x volume = 1 x 0.0098cm3 = 0.0098 moles needed to neutralise the acid
Boots.
5.8 divided by 1000 = 0.0058cm3
Moles of HCl = concentration x volume = 1 x 0.0058cm3 = 0.0058 moles needed to neutralise the acid
Bisodol
13 divided by 1000 = 0.013m3
Moles of HCl = concentration x volume = 1 x 0.013cm3 = 0.013 moles needed to neutralise the acid
Analysis.
All of the above the calculations tables of results and graphs show that Rennie (pepper mint flavour) was definitely the most effective. As I predicted in the above prediction I thought Rennie would be the best and also I predicted that it would be close between Rennie and Bisodol which it was very much so. These results are very close to my initial calculations so therefore this is suggesting that my test was fair and was conducted to an extent of accuracy to give me such results. As you can see in my average table I found that I had got exactly what I predicted for the Rennie tablet which again shows the accuracy of my test.
Evaluation.
I found throughout the experiment and through my results that my experiment must have been conducted well and to such an extent of fairness to get results as close as the predictions. Although this may be the case but it can always be able to be improved.
The accuracy I feel was sufficient because I have spent time on taking down results and observating things when appropriate. This suggests this will be very hard to improve this an only way is to spend even more time observating the results but this may effect the experiment.
As you can see in the above results table there are no anomalous results again therefore suggesting that my experiment was a success and very fair.
I could have improved this test by using a pH probe and a computer program to see when it has exactly reached the pH 1 which would make the test very fair. Also I could have repeated it with a wider range of tablets which may have gave us a wider range in results to compare.
