UNIT 2: Practical Scientific Procedures & Techniques
Learning Aim A: Undertake titration and colorimetry to determine the concentration of solutions
Part 1 (Standardisation of a solution):
Creating a solution with a known concentration
Risk Assessment:
Hazard Risk Precaution Action
Glass Shattering - Handle with care - If glass don’t
touch
Sodium Hydroxide Corrosive - Avoid contact - Wash place of
and Hydrochloric Acid (serious eyes, - Wear goggles irritation with
skin… irritations) water
Standardisation Method:
I measured out 1g of sodium carbonate using a spatula into a weighting boat on a calibrated scale
and then placed it carefully into a clean 250cm3 beaker. After that, I re-weight empty weighting boat
using the same balance and recorded the measurements of before and after (which can be found *).
To ensure that all my solid sodium carbonate has fully transferred I rinsed the weighing boat with
distilled water and poured all of it into the beaker; also using my glass rode to ensure all of it had
been completely dissolve. Once it has been completely dissolved, I transferred the Na2CO3 solution
into a clean 250cm3 volumetric flask (which has been rinsed with distilled water) and rinsed the
beaker as well as the glass rode with water from the wash bottle into the flask to make sure that we
don’t lose any Na2CO3. I then filled up the volumetric flask until the meniscus of the solution was on
the 250 cm³ mark, placed a plug blocking the opening of the volumetric flask. I shook the solution
thoroughly and labelled my name and the exact concentration of my solution.
Mass of weighting boat + Na2CO3 (g) 2.14
Mass of empty weighting boat (g) 1.14
Mass of Na2CO3 used (g) 1
Calculations:
Na2CO3 + HCl → 2NaCl + H2O + CO2
Concentration of Na2CO3 = 1 ÷ 106 = 0.00943 moldm-3
Moles of Na2CO3 in 250cm-3 = 0.00943 ÷ 0.25 = 0.03772
Evaluation:
In the standardisation that’s been perform, we mixed sodium carbonate distilled water to form
sodium hydroxide. While I feel my standardisation went good, I could have prepared and set up for
other titrations during this part.
, Task 2 (HCL and a standard solution):
To find the concentration of hydrochloric acid using sodium carbonate with a known
concentration and methyl orange as the indicator
Equipment list:
• Graduated pipette (25cm3)
• Funnel
• Volumetric Flask (250cm3)
• 2 Beakers (2x250cm3)
• Clamp stand
• Pipette filler
• Distilled water
• Na2CO3 solution
• HCl solution
• Sharpie
• Plug
• Spatula
• Methyl Orange indicator
Calibrate the balance:
Locate the calibration button of the digital scale (“Cal”). Press the button down until the digits
displayed on the scale turn to “0”. Test if the balance had has been calibrated and set it aside to use
later.
Calibrate the pipette:
To calibrate the pipette, I weighed a dry empty beaker and recorded it on my table and then took a
pipette and a pipette filler and measured 25cm3 of distilled water and transferred it into the beaker
and re-weight it.
Mass of empty beaker (g) 50.3
Mass of beaker + 25cm3 water (g) 75.17
Mass of 25cm3 water (g) 24.87
Temperature (°C) 21
Density of water at this temperature 0.997992
Actual volume delivered 24.92
, Calibrate the pH meter:
To calibrate the pH meter you need to place the electro node into a pH7 solution and leave it in
there from approximately one minute. The meter should then state that the solution has a pH of 7, if
not establish the pH meter at that value. After that, rinse the electrode with distilled water and
repeat the process however with pH4 solution.
Titration Method:
To start the titration, you need to pour a little HCl into a beaker, and use the sharpie to label it HCl;
use this to rise the burette and disguard of any waste left. After that, ensure that the tap of the
burette is close and clamp it, then use a clean funnel to pour the dilute HCl into the burette making
sure that the space at the bottom is filled so there is no air bubbles present. Now, label another
beaker Na2CO3 and transfer a small amount of it in there; use this to clean the beaker and pipette
with the help of the pipette filler. After that, rinse your volumetric glass with distilled water and
throw away all your washings, transfer exactly 25cm3 of Na2CO3 solution into the pipette ensuring
that there’s no air bubbles and that the meniscus sits on the graduation line. Then, transfer the
25cm3 into the volumetric flask and add 2-3 drops of methyl orange indicator and place it under the
burette. Place a white tile underneath the volumetric flask to make it easier to detect the colour
change.
To perform the titration, you’ll need recorded the burette start volume in cm³ on your results table.
Open the tap of the burette and continue to swirl the volumetric flask while the HCl is added, and
when you see a colour shift, slow the flow of Na2CO3 into the flask. We're searching for a colour shift
from orange to a mild peach. Then, record the burette end volume after each titration and calculate
the titre, which is the difference between the burette start and end volume. After cleaning all of the
equipment, begin working on the concentration calculation. To determine the concentration,
balance the chemical equation, estimate the moles of Na2CO3, calculate the molar ratio of HCL to
Na2CO3, and then change all of the volume.
yellow → orange → red
(alkali) → (endpoint) → (acid)
Trial Run 1 Run 2 Run 3
Final burette reading (cm3) 17.2 20.5 23.5 23.5
Initial burette reading (cm3) 0 0 0 0
Titre (cm3) 17.2 20.5 23.5 23.5
Learning Aim A: Undertake titration and colorimetry to determine the concentration of solutions
Part 1 (Standardisation of a solution):
Creating a solution with a known concentration
Risk Assessment:
Hazard Risk Precaution Action
Glass Shattering - Handle with care - If glass don’t
touch
Sodium Hydroxide Corrosive - Avoid contact - Wash place of
and Hydrochloric Acid (serious eyes, - Wear goggles irritation with
skin… irritations) water
Standardisation Method:
I measured out 1g of sodium carbonate using a spatula into a weighting boat on a calibrated scale
and then placed it carefully into a clean 250cm3 beaker. After that, I re-weight empty weighting boat
using the same balance and recorded the measurements of before and after (which can be found *).
To ensure that all my solid sodium carbonate has fully transferred I rinsed the weighing boat with
distilled water and poured all of it into the beaker; also using my glass rode to ensure all of it had
been completely dissolve. Once it has been completely dissolved, I transferred the Na2CO3 solution
into a clean 250cm3 volumetric flask (which has been rinsed with distilled water) and rinsed the
beaker as well as the glass rode with water from the wash bottle into the flask to make sure that we
don’t lose any Na2CO3. I then filled up the volumetric flask until the meniscus of the solution was on
the 250 cm³ mark, placed a plug blocking the opening of the volumetric flask. I shook the solution
thoroughly and labelled my name and the exact concentration of my solution.
Mass of weighting boat + Na2CO3 (g) 2.14
Mass of empty weighting boat (g) 1.14
Mass of Na2CO3 used (g) 1
Calculations:
Na2CO3 + HCl → 2NaCl + H2O + CO2
Concentration of Na2CO3 = 1 ÷ 106 = 0.00943 moldm-3
Moles of Na2CO3 in 250cm-3 = 0.00943 ÷ 0.25 = 0.03772
Evaluation:
In the standardisation that’s been perform, we mixed sodium carbonate distilled water to form
sodium hydroxide. While I feel my standardisation went good, I could have prepared and set up for
other titrations during this part.
, Task 2 (HCL and a standard solution):
To find the concentration of hydrochloric acid using sodium carbonate with a known
concentration and methyl orange as the indicator
Equipment list:
• Graduated pipette (25cm3)
• Funnel
• Volumetric Flask (250cm3)
• 2 Beakers (2x250cm3)
• Clamp stand
• Pipette filler
• Distilled water
• Na2CO3 solution
• HCl solution
• Sharpie
• Plug
• Spatula
• Methyl Orange indicator
Calibrate the balance:
Locate the calibration button of the digital scale (“Cal”). Press the button down until the digits
displayed on the scale turn to “0”. Test if the balance had has been calibrated and set it aside to use
later.
Calibrate the pipette:
To calibrate the pipette, I weighed a dry empty beaker and recorded it on my table and then took a
pipette and a pipette filler and measured 25cm3 of distilled water and transferred it into the beaker
and re-weight it.
Mass of empty beaker (g) 50.3
Mass of beaker + 25cm3 water (g) 75.17
Mass of 25cm3 water (g) 24.87
Temperature (°C) 21
Density of water at this temperature 0.997992
Actual volume delivered 24.92
, Calibrate the pH meter:
To calibrate the pH meter you need to place the electro node into a pH7 solution and leave it in
there from approximately one minute. The meter should then state that the solution has a pH of 7, if
not establish the pH meter at that value. After that, rinse the electrode with distilled water and
repeat the process however with pH4 solution.
Titration Method:
To start the titration, you need to pour a little HCl into a beaker, and use the sharpie to label it HCl;
use this to rise the burette and disguard of any waste left. After that, ensure that the tap of the
burette is close and clamp it, then use a clean funnel to pour the dilute HCl into the burette making
sure that the space at the bottom is filled so there is no air bubbles present. Now, label another
beaker Na2CO3 and transfer a small amount of it in there; use this to clean the beaker and pipette
with the help of the pipette filler. After that, rinse your volumetric glass with distilled water and
throw away all your washings, transfer exactly 25cm3 of Na2CO3 solution into the pipette ensuring
that there’s no air bubbles and that the meniscus sits on the graduation line. Then, transfer the
25cm3 into the volumetric flask and add 2-3 drops of methyl orange indicator and place it under the
burette. Place a white tile underneath the volumetric flask to make it easier to detect the colour
change.
To perform the titration, you’ll need recorded the burette start volume in cm³ on your results table.
Open the tap of the burette and continue to swirl the volumetric flask while the HCl is added, and
when you see a colour shift, slow the flow of Na2CO3 into the flask. We're searching for a colour shift
from orange to a mild peach. Then, record the burette end volume after each titration and calculate
the titre, which is the difference between the burette start and end volume. After cleaning all of the
equipment, begin working on the concentration calculation. To determine the concentration,
balance the chemical equation, estimate the moles of Na2CO3, calculate the molar ratio of HCL to
Na2CO3, and then change all of the volume.
yellow → orange → red
(alkali) → (endpoint) → (acid)
Trial Run 1 Run 2 Run 3
Final burette reading (cm3) 17.2 20.5 23.5 23.5
Initial burette reading (cm3) 0 0 0 0
Titre (cm3) 17.2 20.5 23.5 23.5
