The aim of the experiment is to find out which indigestion tablet is the best. We can do this by looking at how much alkali is put in after the tablet has been put in.

Method

1. Put a crushed tablet into a volumetric flask and then add acid to the tablet in the volumetric flask until it reads 250cm3.
2. Wait until the tablet and acid forms a solution.
3. Take out 25cm3 of the solution with a pipette and put it into a conical flask.
4. Now add a few drops of Phenolphthalein to the solution.
5. Put some of the alkali (Sodium Hydroxide) into the burette and record how much of the alkali you have put into the burette, with a funnel.
6. Start to add the alkali to your solution, but only in a few drops at a time because if you put in too much, the solution won’t be neutralised and the pH will go over pH7.
7. Add the alkali until it is a light pink colour.
8. Write down the finishing point of the liquid (up to where the meniscus is) and calculate how much alkali has been used by subtracting the finishing point from the starting point.
9. Repeat the steps from 1–8 another two times for the same tablet and do the experiment three times or more for each tablet you do, to get accurate results.
10. Compare all the results by putting them in a table then transforming it into a graph. The tablet that has used the least amount of alkali is the best tablet as it had already neutralised most of the aid before the alkali was added.

Fair test table

Results

Analysis

My results

Class Results

The next few paragraphs show the moles of each of the tablets and also with the different concentrations.

The calculation for the number of moles is:

Moles of Alkali = x = amount of alkali

25cm3 of the mixture = x/1000 * 0.1 moldm-3 = y moles

250cm3 of the mixture = y * 10 = z moles

Starting amount of acid = 250/1000 * (the concentration) = v moles

To find out how much reacted with the tablet = V – Z = R Moles (the acid used)

The number of moles in each tablet.

Tablet: Peppermint

Concentration: 0.1

Calculation:

X = 17.87142857/1000 * 0.1 = 0.00178142

Z = 0.00178142 * 10 = 0.0178142

V = 250/1000 * 0.1 0.025

R = 0.025 – 0.0178142 = 0.0071858 Moles

Number of moles = 0.0071858 Moles

Tablet: Peppermint

Concentration: 0.5

Calculation:

X = 4.766666667/1000 * 0.1 = 0.0004766666667

Z = 0.000466666667 * 10 = 0.004766666667

V = 250/1000 * 0.5 = 0.125

R = 0.125 – 0.004766666667 = 0.120233333 Moles

Number of moles = 0.120233333 Moles

Tablet: Rennie

Concentration: 0.1

Calculation:

X = 10.1 * 0.1 = 0.00101

Z = 0.00101 * 10 = 0.0101

V = 250/1000 * 0.1 = 0.025

R = 0.25 – 0.0101 = 0.2399 Moles

Number of Moles = 0.2399 Moles

Tablet: Rennie

Concentration: 0.5

Calculation:

X = 22.76/1000 * 0.1 = 0.002276

Z = 0.002276 * 10 = 0.02276

V = 250/1000 * 0.5 = 0.125

R = 0.125 – 0.02276 = 0.10224

Number of Moles = 0.10224

Tablet: Settlers

Concentration: 0.1

Calculation:

X = 22.53333333/1000 * 0.1 = 0.002253333333

Z = 0.002253333333 * 10 = 0.022533333

V = 250/1000 * 0.1 = 0.125

R = 0.025 – 0.022533333 = 0.2246667 Moles

Number of Moles = 0.2246667 Moles

Tablet: Settlers

Concentration: 0.5

Calculation:

X = 13/1000 * 0.1 = 0.0013

Z = 0.0013 * 10 = 0.013

V = 250/1000 * 0.5 = 0.125

R = 0.125 – 0.013 = 0.112 Moles

Number of Moles = 0.112 Moles

The results that I have chosen to use are my class results. I am using these because in my group we weren’t able to collect enough results to compare them with each other, as some of our experiments went wrong. We added too much alkali and the solution went over the neutralisation point.

When I looked at the table in which my class results are, I could see that for all three of the tablets and the different concentrations as well, the neutralisation points were very close. When the concentration was 0.1, the settlers tablet the results were actually within the number and they were only 0.1cm3 away from each other. But the best tablet was the Rennie because it had used the lowest amount of alkali each time even though the results had been spread out into two numbers. The one in this experiment that was second best was the peppermint tablet. But the problem with this tablet was that the results weren’t reliable because they were spread out over a large amount of numbers, even though some of the volumes of the alkalis were the same.

In the 0.5 concentrations, the peppermint tablet was the best to use. Then came the settlers and last of all came the Rennie. But I think that these results are not reliable because there are many more results taken down in the 0.1 concentrations than in the 0.5 concentrations. Also because they are only done by one pair of people in each of the tablets and they were done many times by those pairs.

Many of our results didn’t fit the pattern. There are two reasons for this. One of them is that we used different alkalis that had different concentrations. The other reason is that there were lots of people in the class and each one of the groups did the experiment in their own way and everybody didn’t do it in the same order.

I think that we should have been given a little bit more time to complete the experiment, so we could have got more results and more people could have got on to doing all of the tablets instead of just one or two of the tablets. We would have been able to work with our own results. The results don’t prove our point as well because two different types of concentrations have been used both of them have come out with different views to the other one.

Evaluation

If I were to do this experiment and this piece of coursework again, then I would make sure that I used only one type of concentration, made sure that I collected more results so I would only be able to use my results so they would be reliable, and I would also do things more accurately, like make sure that all of the tablet had gone into the conical flask after I had crushed it and that most of it had not just stuck to the side of the crusher or the bowl that I was crushing it in.