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Distinction - BTEC Applied Science Unit 2 LA A- Learning aim A: Undertake titration and colorimetry to determine the concentration of solutions.£8.49
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Introduction:
In this experiment, I will undertake titration and colorimetry to determine the concentration of
solutions, making sure that all the equipment is calibrated and cleaned before and after
being used. I will prepare a standard solution, prepare standardisation of HCl, carry out
titration of sodium hydroxide with HCl (using Phenolphthalein indicator) and determine the
concentration of copper (II) sulphate solution by colorimetry. I will also have to calculate the
concentration of HCl after standardisation and NaOH after carrying out titration.
Prepare a standard solution and standardisation of Sodium Carbonate:
Equipment:
● Balance
● Funnel
● Distilled water
● Volumetric flask
● Sodium carbonate
● Weighing boat
● Solid sodium hydroxide
Method to prepare a standard solution:
1. Calibrate the weighing balance that will be used.
2. Place the weighing boat on the balance and press the Tare button so the display
shows 0.0000 grams (decimal places will depend on the balance).
3. Weigh the anhydrous sodium carbonate between 1.25 and 1.45g.
4. Gently transfer the sodium carbonate to a beaker, recording the measurements
accurately and precisely to establish the exact mass transferred.
5. Fill the beaker with 150 cm3 of distilled water then stir to completely dissolve the
sodium carbonate.
6. Carefully and precisely transfer all of the solution to a 250 cm3 volumetric flask and top
up with more distilled water to make the solution 250 cm3.
Method to prepare the standardisation of an acid (HCl):
1. Calibrate the pipette that is going to be used.
2. Pour 25 cm3 of sodium carbonate solution into a 250 cm3 conical flask, along with a
few drops of phenolphthalein indicator using a pipette.
3. Clean and fill a burette (50 ml) with a hydrochloric acid solution with a concentration
of around 0.1 M.
4. Add the hydrochloric acid to the sodium carbonate solution and titrate until the
indicator changes the colour of the solution.
1
, Unit 2 LA A Titrations name
5. Record all measurements accurately and precisely to calculate the exact amount of
hydrochloric acid needed to reach the titration’s end point.
6. Repeat the experiment 3 times to get more reliable results.
A.P1 Part
Risk assessment:
● Sodium hydroxide solution: they are highly corrosive, causing irritation of the eyes. To
prevent this, goggles and gloves must be worn to protect the eyes and the skin
respectively. If it goes in the eyes, for at least 20 minutes, immerse the eye in softly
running tap water. Seek advice from a doctor. If a trip to the hospital is essential, keep
washing the eye during the ambulance ride. If it is split on the skin or clothes, dispose
of any contaminated clothing (if possible). After that, soak the skin with a large
amount of water. Consult a doctor if a big area is affected or blistering occurs. If it is
split on the floor, stools, etch then wipe away small amounts with a moist towel and
thoroughly rinse. Cover with mineral absorbent (e.g., cat litter) and scoop into a
bucket for larger amounts, especially for (moderately) concentrated solutions. Citric
acid can be used to balance things out. Rinse well with water.
● Broken glassware can cause cuts in the skin, to prevent this, check the glassware
before their use, put the equipment in the middle of the table instead of the edge. If a
glassware was damaged before using them, replace it. The glassware should be
handled carefully and properly.
Results (calculation of moles in HCl):
Volumes in cm3 Rough 1st trial 2nd trial 3rd trial
Initial volume 0.00 0.00 0.00 0.00
Final volume 14.80 14.40 14.70 14.60
Volume of HCl used 14.80 14.40 14.70 14.60
Average volume of HCl used 14.57 14.57 14.57
Average volume used in cm3 = (14.40+14.70+14.60)/3 = 14.5666666667 cm3 = 14.57 cm3
Mass for Na2CO3= 23x2+12+16x3= 106
1.255g of Na2CO3 used so, number of moles= 1.255/106= 0.01183962264 moles in 250cm3
Equation for the reaction: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
Moles of Na2CO3 in 25 cm3= 0.01183962264/10= 0.00118396226
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