Super Soap Investigation

Safety

In order to keep the experiment safe I will have to follow a number of rules:

* Firstly all bags and coats should be put out of the way (at the back of the class) not to cause an obstruction when performing the experiment.

* Seats will have to be put under the tables and so the investigation will have to be followed while standing up.

* Before starting the experiment and before any chemicals are brought out, goggles must be put on. This is to ensure that no chemicals or foreign objects get into the eyes and cause damage.

Apparatus

To complete the experiment I will need a number of apparatus:

* 25cm3 of sodium hydroxide

* 50cm3 of hydrochloric acid

* Burette

* Clamp

* Conical Flask

* Pipette

* Pipette Filler

* Indicator - Phenolphthalein

* Distilled Water

* Funnel

Pre-Test

I need to conduct a pre-test for two reasons. The first being to find out the colour changes of the indicator when neutralisation is taking place and secondly, to find out approximately how much hydrochloric acid is needed to neutralise the sodium hydroxide.

Pre-Test Plan

. Follow all safety regulations

2. Collect all apparatus

3. Clean out apparatus with distilled water

4. Rinse the burette through with hydrochloric acid and rinse the pipette through with sodium hydroxide to prepare the apparatus to use the solution because any remaining distilled water in the apparatus may dilute the acid or alkali.

5. Use the pipette to put 25cm3 of sodium hydroxide into the conical flask and label it.

6. Use a funnel to put 50cm3 of hydrochloric acid into the burette.

7. Carefully put five drops of phenolphthalein into the conical flask with the sodium hydroxide.

8. Slowly start to release hydrochloric acid from the burette by turning the tap and into the conical flask now containing sodium hydroxide and the indicator.

9. Note the colour change of the indicator at the point of neutralisation.

Pre-Test Results

When indicator was added to the sodium hydroxide, the solution changed from colourless to pink. When 43cm3 of hydrochloric acid was released into the sodium hydroxide and indicator, the solution turned from pink to colourless again. By the solution turning colourless again, this shows that the solution is now neutralised.

Plan

I will have to follow some sort of method to try and perform the experiment in order to obtain the highest standards of accuracy and reliability.

. Firstly follow out all safety regulations as stated earlier.

2. Collect all of the apparatus listed.

3. Use distilled water to clean out all of the apparatus because there may be ions left in the burette or pipette as the distilled water is deionised so there will be no ions there for the hydroxide to react with.

4. Rinse the burette through with hydrochloric acid and then rinse the pipette through with sodium hydroxide. This is to prepare the apparatus to use the solution because the remaining distilled water may dilute the acid or alkali.

5. Use the pipette to place 25cm3 of sodium hydroxide into the conical flask and label the flask

6. Now put five drops of phenolphthalein, which I am using as an indicator, into the conical flask with the sodium hydroxide. The solution will then turn pink

7. Start to release hydrochloric acid from the burette by turning the tap into the conical flask with the sodium hydroxide and indicator and stir the solution continuously.

8. Continue to slowly add hydrochloric acid until when stirred, the solution has become clear or colourless. When this occurs, the solution has been neutralised.

9. Record in a table the amount of hydrochloric acid it took to neutralise the sodium hydroxide.

Results Table

Reading at Start (cm3)

Reading at End (cm3)

Titre (cm3)

0

41.2

41.2

0

40.9

40.9

0

38.7

38.7

0

37.4

37.4

0

37.2

37.2

0

36.7

36.7

0

36.7

36.7

7

43.6

36.6

The results which have been bracketed are the results which are most alike with there being just a 0.1cm3 difference.

Analysis

I found out that, to neutralise 25cm3 of sodium hydroxide it took an average 36.7cm3 of hydrochloric acid of 0.1m.

From this I found out the concentration of the sodium hydroxide which is:

Concentration of NaOH = Vol HCl x Conc HCl

Vol NaOH

Concentration of NaOH = 36.7/1000 x 0.1

25/1000

Concentration of NaOH = 0.1468moldm3

Evaluation

When looking at my results I consider them to be accurate. This is because, even though my results at the beginning weren't very similar, I think this was because of my slow reactions when turning off the tap. As I started to get used to the experiment and was more aware of when the neutralisation reaction was about to take place, my own reactions got quicker and my end results were very accurate being just 0.1cm3 apart. You can notice how the titre gets smaller as my reactions get quicker.

When I conducted the experiment, I think it was reliable because, as I mentioned before, my end results were very similar and close together. They were 36.7, 36.7 and 36.6. Although my results at the end were reliable, there may have been errors in the experiment which could have made it unreliable. When I rinsed out the conical flask with water, the water droplets which may have still been in the flask when the sodium hydroxide was added could have affected its concentration by diluting it. This would then have affected the volume of concentration of hydrochloric acid it took to neutralise the sodium hydroxide. To solve this problem I should have wiped the conical flask thoroughly with a paper towel this would have ensured that no water droplets would be contained in the flask.

Another thing that could have affected the results was my own reactions when it came to turning off the tap of the burette to stop the hydrochloric acid coming out. There is not a great deal that I would be able to do about that to improve it apart from carrying out the experiment numerous times to try and get my fastest reactions possible. I could have also recorded the results to two decimal places instead of one to improve the accuracy of the experiment.