Unit 2: Practical scientific procedures and techniques
Learning aim A: undertake titration to determine the concentration of solutions
Aims:
To find the concentration of an unknown solution of sodium hydroxide
(NaOH)
To find the endpoint of the reaction (when the solution becomes neutral)
by using correct and appropriate equipment/indicators
Find the concentration of hydrochloric acid by titrating it against a standard
solution of sodium carbonate (Na2CO3)
Calibration of a balance
Equipment List:
Weighing boat
Balance/scale
Weights/known masses
Tweezers
Method:
1. Plug in and turn on the balance, let the balance warm up. It needs to reach
thermal equilibrium.
2. Check for correct levelling, surfaces should be flat so that the exact reading
can be achieved.
3. Set the balance to 0.00 before placing the weighing boat, this is to avoid
zero errors that affect the results. Record the mass of the weighing boat.
, 4. Add a 10g mass to the balance, record the results. Weigh a total of three
times.
5. Repeat using 20g, 30g, 40g, 50g weights and calculate an average for each.
Problems or issues:
There were not many major issues that impacted the experiment, however there
were confounding variables to look out for. For instance, anomalous results had
to be removed from the experiment as it would affect the average of the data
collected.
Accuracy, Precision, and Reliability:
Accuracy: The results were close to the true value. This is because results were
not more than 1g or less than 0.5g away from the true value of 10g.
Precision: At least three trials were done and results were precise as the
measurements were close together.
Reliability: The results were reliable as they were quite close to each other.
Hazards and risks:
The weights used were slightly heavy, they could have caused harm if dropped or
mishandled. To prevent this, handle all equipment used with care.
Improvements:
, To improve the experiment, use a balance that can weigh more than 4 decimal
places. This would ensure that results are accurate and that not many errors are
made.
Results: Table showing weights of different masses
Known 1st 2nd 3rd Average mass
masses (g) (g)
10g 10.07 10.07 10.07 10.07
20g 20.04 20.03 20.03 20.03
30g 30.10 30.09 30.09 30.09
40g 40.24 40.24 40.24 40.24
50g 50.32 50.32 50.32 50.32
Justification/Evaluation:
Due to calibrating the balance, the results were precise and no calculations were
needed to improve the results. The results were within range making it reliable.
Calibrating a balance is essential as properly calibrated balances give accurate
results and decreases probability of a weighing mistake which can cost extra time
and money. In industry, incorrectly calibrated equipment can lead to production
problems such as unscheduled downtime.
Calibration of volumetric pipette:
Equipment:
Beaker
Volumetric pipette
Distilled water
Pipette filler
Learning aim A: undertake titration to determine the concentration of solutions
Aims:
To find the concentration of an unknown solution of sodium hydroxide
(NaOH)
To find the endpoint of the reaction (when the solution becomes neutral)
by using correct and appropriate equipment/indicators
Find the concentration of hydrochloric acid by titrating it against a standard
solution of sodium carbonate (Na2CO3)
Calibration of a balance
Equipment List:
Weighing boat
Balance/scale
Weights/known masses
Tweezers
Method:
1. Plug in and turn on the balance, let the balance warm up. It needs to reach
thermal equilibrium.
2. Check for correct levelling, surfaces should be flat so that the exact reading
can be achieved.
3. Set the balance to 0.00 before placing the weighing boat, this is to avoid
zero errors that affect the results. Record the mass of the weighing boat.
, 4. Add a 10g mass to the balance, record the results. Weigh a total of three
times.
5. Repeat using 20g, 30g, 40g, 50g weights and calculate an average for each.
Problems or issues:
There were not many major issues that impacted the experiment, however there
were confounding variables to look out for. For instance, anomalous results had
to be removed from the experiment as it would affect the average of the data
collected.
Accuracy, Precision, and Reliability:
Accuracy: The results were close to the true value. This is because results were
not more than 1g or less than 0.5g away from the true value of 10g.
Precision: At least three trials were done and results were precise as the
measurements were close together.
Reliability: The results were reliable as they were quite close to each other.
Hazards and risks:
The weights used were slightly heavy, they could have caused harm if dropped or
mishandled. To prevent this, handle all equipment used with care.
Improvements:
, To improve the experiment, use a balance that can weigh more than 4 decimal
places. This would ensure that results are accurate and that not many errors are
made.
Results: Table showing weights of different masses
Known 1st 2nd 3rd Average mass
masses (g) (g)
10g 10.07 10.07 10.07 10.07
20g 20.04 20.03 20.03 20.03
30g 30.10 30.09 30.09 30.09
40g 40.24 40.24 40.24 40.24
50g 50.32 50.32 50.32 50.32
Justification/Evaluation:
Due to calibrating the balance, the results were precise and no calculations were
needed to improve the results. The results were within range making it reliable.
Calibrating a balance is essential as properly calibrated balances give accurate
results and decreases probability of a weighing mistake which can cost extra time
and money. In industry, incorrectly calibrated equipment can lead to production
problems such as unscheduled downtime.
Calibration of volumetric pipette:
Equipment:
Beaker
Volumetric pipette
Distilled water
Pipette filler
