Assignment 2A
In this assessment I had to determine the concentration of an unidentified sodium hydroxide (NaOH) sample for this evaluation.
In order to do this, I had to titrate the hydrochloric acid (HCl) against a standard sodium carbonate solution (Na2CO3) in order to
figure out its concentration.
In this assignment, I conducted an acid-base titration to determine the concentration of sodium hydroxide (NaOH) using
hydrochloric acid (HCl). The titration is based on the principle of neutralisation, where the hydroxide ions (OH⁻) from NaOH
react with hydrogen ions (H⁺) from HCl to form water and sodium chloride (NaCl):
NaOH+HCl→NaCl+H2O
This reaction occurs in a 1:1 molar ratio, which simplifies the calculation of the NaOH concentration from the volume and
molarity of HCl used.
In acid-base titrations, the equivalence point is when the amount of acid added matches exactly the amount of base present, or
vice versa. For titrations involving a strong acid like HCl and a strong base like NaOH, this point occurs at pH 7, which is
neutral. It indicates that all the acid has been neutralised by the base, or all the base has been neutralised by the acid.
As the titration progresses, the pH of the solution changes depending on whether more acid or base is added. Initially, the pH
starts low because of the excess of HCl. When NaOH is added, the hydroxide ions (OH⁻) from NaOH react with the hydrogen
ions (H⁺) from HCl, causing the pH to rise. Near the equivalence point, there is a rapid increase in pH, showing us that the
reaction is almost complete and neutralisation is about to occur.
As I did the titration, I saw the solution start to turn light pink when I added NaOH, showing that neutralisation was almost done.
When the solution stayed pink for a bit longer, it meant the reaction had finished. This matched what I expected for the pH and
showed that phenolphthalein worked well as an indicator.
To sum up, understanding how acid-base titrations work, picking the right indicator based on pH, and doing the experiment
carefully all help find the concentration of NaOH accurately. This shows how well I can apply what I learn in labs.
Equipment Used:
- Beaker
- 100cm3 measuring cylinder
- Weighing boat
- Filter paper
- Distilled water
- 250cm3 Volumetric flask
- Bulb Pipette
- Funnel
- Anhydrous sodium carbonate
Before starting the experiment, we calibrated our experiment to ensure we got the most accurate results; this is how to calibrate
a volumetric pipette:
1. Clean the pipette with distilled water.
2. Weigh an empty vessel and record its mass.
3. Fill the pipette to the calibration mark with distilled water.
4. Dispense the water into the vessel.
5. Weigh the vessel with the water and record the mass.
6. Measure the temperature of the water.
7. Calculate the mass of the water by subtracting the empty vessel's mass from the filled vessel's mass.
8. Refer to a water density chart to find the density at the measured temperature.
9. Calculate the volume of the water by dividing the mass by the density.
10. Compare the calculated volume with the pipette's nominal volume.
11. Repeat the process multiple times for accuracy.
Calibration of pH probe - Calibration of the pH Probe Begin by connecting the probe's connector to the data logger port.
Attach the pH probe to the connector, then press the metres until the screen activates and releases. Select 'sensor config' and
proceed to calibrate the sensor. Ensure the 'use 3. Calibration' box is unchecked. Enter 7.0 in the first test box and 9.0 in the
last test box, then click 'next'. Dip the pH probe into the pH 7 solution and wait for the readings to stabilise. After this,
disconnect the probe, shake off any residue, rinse with distilled water, and repeat the calibration process with the next pH
solution.
In this assessment I had to determine the concentration of an unidentified sodium hydroxide (NaOH) sample for this evaluation.
In order to do this, I had to titrate the hydrochloric acid (HCl) against a standard sodium carbonate solution (Na2CO3) in order to
figure out its concentration.
In this assignment, I conducted an acid-base titration to determine the concentration of sodium hydroxide (NaOH) using
hydrochloric acid (HCl). The titration is based on the principle of neutralisation, where the hydroxide ions (OH⁻) from NaOH
react with hydrogen ions (H⁺) from HCl to form water and sodium chloride (NaCl):
NaOH+HCl→NaCl+H2O
This reaction occurs in a 1:1 molar ratio, which simplifies the calculation of the NaOH concentration from the volume and
molarity of HCl used.
In acid-base titrations, the equivalence point is when the amount of acid added matches exactly the amount of base present, or
vice versa. For titrations involving a strong acid like HCl and a strong base like NaOH, this point occurs at pH 7, which is
neutral. It indicates that all the acid has been neutralised by the base, or all the base has been neutralised by the acid.
As the titration progresses, the pH of the solution changes depending on whether more acid or base is added. Initially, the pH
starts low because of the excess of HCl. When NaOH is added, the hydroxide ions (OH⁻) from NaOH react with the hydrogen
ions (H⁺) from HCl, causing the pH to rise. Near the equivalence point, there is a rapid increase in pH, showing us that the
reaction is almost complete and neutralisation is about to occur.
As I did the titration, I saw the solution start to turn light pink when I added NaOH, showing that neutralisation was almost done.
When the solution stayed pink for a bit longer, it meant the reaction had finished. This matched what I expected for the pH and
showed that phenolphthalein worked well as an indicator.
To sum up, understanding how acid-base titrations work, picking the right indicator based on pH, and doing the experiment
carefully all help find the concentration of NaOH accurately. This shows how well I can apply what I learn in labs.
Equipment Used:
- Beaker
- 100cm3 measuring cylinder
- Weighing boat
- Filter paper
- Distilled water
- 250cm3 Volumetric flask
- Bulb Pipette
- Funnel
- Anhydrous sodium carbonate
Before starting the experiment, we calibrated our experiment to ensure we got the most accurate results; this is how to calibrate
a volumetric pipette:
1. Clean the pipette with distilled water.
2. Weigh an empty vessel and record its mass.
3. Fill the pipette to the calibration mark with distilled water.
4. Dispense the water into the vessel.
5. Weigh the vessel with the water and record the mass.
6. Measure the temperature of the water.
7. Calculate the mass of the water by subtracting the empty vessel's mass from the filled vessel's mass.
8. Refer to a water density chart to find the density at the measured temperature.
9. Calculate the volume of the water by dividing the mass by the density.
10. Compare the calculated volume with the pipette's nominal volume.
11. Repeat the process multiple times for accuracy.
Calibration of pH probe - Calibration of the pH Probe Begin by connecting the probe's connector to the data logger port.
Attach the pH probe to the connector, then press the metres until the screen activates and releases. Select 'sensor config' and
proceed to calibrate the sensor. Ensure the 'use 3. Calibration' box is unchecked. Enter 7.0 in the first test box and 9.0 in the
last test box, then click 'next'. Dip the pH probe into the pH 7 solution and wait for the readings to stabilise. After this,
disconnect the probe, shake off any residue, rinse with distilled water, and repeat the calibration process with the next pH
solution.
