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Funnel - for pouring liquids into containers with small openings
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3x Flask - a container, such as a narrow-necked vessel of glass for containing liquid
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distilled water - Water from which all minerals and other impurities have been removed by the process of distillation
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Sodium hydroxide - Highly active alkaline
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Phenolphthalein - Phenolphthalein is a sensitive pH indicator with the formula C20H14O4. Often used in titrations, it turns from colourless in acidic solutions to pink in basic solutions, the colour change occurring between pH 8 and pH 10.
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Burette - measuring instrument consisting of a graduated glass tube with a tap at the bottom; used for titration
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Gastric juice - acid made in the stomach that works with pepsin and other enzymes to break down proteins
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Pipette - Glass or transparent plastic tube used in measuring or transferring small amounts of liquid
Picture of Apparatus
Flask distilled water Sodium hydroxide
Clamp Stand Burette
Phenolphthalein
Health and safety
In the lab you must be aware to work safely in the lab for you and other around you in the labs. You must always wear a lab coat and if you have long hair it must be tie back away any chemicals or open flames also you need to wear safety glasses and glove to protect you eyes and skin if handling dangerous chemicals in addition no eating or drinking as well as you are not to bring your bags into the lab as it is an obstruction and a safety hazard.
In my experiment I will be using dangerous chemicals therefore I made a risk assessment table tell me what the hazard are and control measure are if any thing dose go wrong
Method
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Add 25cm3 of hydrochloric acid in to a conical flask using a pipette.
- Fill the burette to the with sodium hydroxide Take the initial readings of the burette and record them on to a table.
- Add 1 to 2 drops of phenolphthalein indicator in to the conical flask
- Titrate the hydrochloric acid in the conical flask against the sodium hydroxide solution from the burette.
- While titrating use the white tile, place it underneath the conical flask, so it helps you to see the end point. The end point is when the colour of the solution turns pink. Aim to get a slight touch of pink, and not a dark colour.
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Take reading off the burette once you have got the end point, and try to read it to the nearest 0.01cm3 record the reading on to a table.
- Repeat procedure at least 2 more times
- After repeating the experiment. Clean and dry the pipettes and the conical flask.
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Repeat the whole experiment following, procedures but now using 25cm3 hydrochloric acid in the conical flask, have 25cm3 gastric juice.
- Record the results on to a table again and do the calculations.
Results and calculation
1. Titration data for the standardisation of sodium hydroxide with 25 cm3 0.01 mol dm-3 HCL
Average Volume of sodium hydroxide solution used – 31.3cm3
(31 + 31.6 + 31.4 / 3 = 31.3)
Number of moles of NaOH present in this volume – 2.5 x 10-4
(25cm3 / 1000 x 0.01 = 2.5 x 10-4)
Therefore: Molar concentration of NaOH – 7.9872 x 10-6
(2.5 x 10-4 / 31.3 = 7.9872 x 10-6)
2. Titration data for 25cm3 gastric juice with the standardized solution of NaOH
Average volume of sodium hydroxide solution used - 40.5 cm3
(40.6 + 40.7 + 40.3 = 40.5)
Number of moles of NaOH present in this volume – 6.2 x 10-6 moles
(2.5 x 10-4 / 40.5 = 6.2 x 10-6)
Therefore number of moles of HCL in 25cm3 of gastric juice - 6.2 x 10-6 moles
Therefore molar concentration of HCL in gastric juice – 0.01 mol dm-3
(1000/25 x 2.5 x 10-4 = 0.01)
Concentration of hydrogen ions in gastric juice - 0.01 mol dm-3
The measured pH value of the gastric juice = 1.99
Using the - Log10 on the calculator I am able to calculate the pH level that I got
pH = - Log10 (molar concentration of H+)
= -Log (0.01) = 2pH
Discussion
As you can see form my results the reading that I got form my results was constant and have a trend. During the experiment human error may have been made such as not reading off the buttue acutely as the buttue was not eye level so it was hard to see what the reading was also filling up the piptle to where the mark is to make accurate as well as other human error that may have caused inaccurate result
Despite all of this as you can see the results that I have obtained are constant and do have trend and pattern so I am happy to say that my results are as accurate as can be
The things that will to improve if I was doing this experiment again is to work more acutely if I see the there is no trend of pattern in result is to repeat the whole experiment again to see if I get a less variable result. Other thing which I will improve on is to clean the glassware properly so the is no contamination and so my result do not vary
Conclusion
In this experiment I had two aim to complete which where
Aim 1
To determine the number of moles of sodium hydroxide in hydrochloric acid.
I believe that I completed successfully. having completed aims with results which was
Average Volume of sodium hydroxide solution used – 31.3cm3
(31 + 31.6 + 31.4 / 3 = 31.3)
Number of moles of NaOH present in this volume – 2.5 x 10-4
(25cm3 / 1000 x 0.01 = 2.5 x 10-4)
Therefore: Molar concentration of NaOH – 7.9872 x 10-6
(2.5 x 10-4 / 31.3 = 7.9872 x 10-6)
Aim 2
To determine the number of moles of sodium hydroxide present in gastric.
Once again I completed successfully. having completed aims with results which was
Average volume of sodium hydroxide solution used - 40.5 cm3
(40.6 + 40.7 + 40.3 = 40.5)
Number of moles of NaOH present in this volume – 6.2 x 10-6 moles
(2.5 x 10-4 / 40.5 = 6.2 x 10-6)
Therefore number of moles of HCL in 25cm3 of gastric juice - 6.2 x 10-6 moles
Therefore molar concentration of HCL in gastric juice – 0.01 mol dm-3
(1000/25 x 2.5 x 10-4 = 0.01)
Concentration of hydrogen ions in gastric juice - 0.01 mol dm-3
Overall I believe this experiment went very well and I have lean a lot in being accrued and precise and next time round when I am doing this experiment I should be even better at it.
