Unit 2- Practical Scientific Procedures and Techniques
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Btec Applied Science
Unit 2a : Standard Solutions and Titrations
Unit 2a : Standard Solutions and Titrations
In this assignment I will be writing 2 reports on titrations and colorimetry. We did
these experiments in class so that we could have hands-on experience of how they
worked. To begin with, we calibrated all of our equipment.
Calibrating a balance:
The definition of calibration is to “correlate the readings of an instrument with those
of a standard in order to check the instruments accuracy”. [1] The first calibration we
carried out was on an analytical balance. We did this by pressing the tare button,
which sets the scale to zero, and then experimenting with different known masses.
For example, after we had set it to zero, we placed a 10 gram weight onto the
balance and then waited for the reading.
Our results:
We found that each time we did this with different weights, our reading was always
0.008 out. We had to take this into account when we were creating our standard
solution.
Calibrating a thermometer:
To calibrate our liquid thermometer, we used 150ml of distilled water for the boiling
thermometer test and 3 ice cubes for the freezing point thermometer test. We used
the same thermometer for both tests, but waited for it to return to room temperature
before starting the next test.
For the boiling test we followed this method:
1. Measure 150ml of distilled water in a measuring cylinder and pour into a
beaker
2. Set up a bunsen burner and a tripod with a heat mat on top of it
3. Place the beaker with the water in it on top of the tripod and turn on the
bunsen burner
4. Hold the thermometer in the water (double check the thermometer is at room
temperature before doing this)
5. Wait for the water to show signs of boiling (eg bubbling, steaming)
6. Check the reading on the thermometer
7. When the water has reached boiling point, the thermometer should read
100℃
1
,Btec Applied Science
Unit 2a : Standard Solutions and Titrations
For the freezing test we followed this method:
1. Place 3 ice cubes in a beaker
2. Check the thermometer is at room temperature and then place it into the ice
cubes
3. Gently swirl the thermometer around the ice cubes until the reading states
that it is at 0℃
Our results:
Type of instrument Ice reading (℃) Boiling reading (℃)
Liquid thermometer 0℃ 100℃
2
, Btec Applied Science
Unit 2a : Standard Solutions and Titrations
Calibrating a measuring cylinder:
To calibrate our measuring cylinder, we used a measuring scale, water, beaker, and
the measuring cylinder. The method we followed was:
1. Place the beaker on the measuring scale and tare it to zero
2. Add water to the beaker on the scale and stop when it reads 100g
3. Pour this water into the measuring cylinder and measure how accurate it is.
Our results:
The water in our measuring cylinder reads as 102, therefore it is out by 2.
Calibrating a pipette:
We calibrated our pipettes before doing the titration to maintain the accuracy of the
instrument. We calibrated a volumetric pipette of 25㎤. We did this by following this
method:
1. Run deionized water through your pipette
2. Dry the outside of the pipette with a paper towel
3. Check to make sure that there are no water droplets in the pipette - if there is
it means it needs to be cleaned
4. Record the temperature of the room
5. Place a beaker on to a balance and tare it to zero
6. Using your pipette, draw enough water to the 25㎤ line
7. Gently dry the pipette with a paper towel
8. Transfer this water into the beaker on the balance
9. There will be some residue left in the tip of the pipette, this is due to surface
tension
10. Record the mass the balance reads (g)
11. If the pipette is accurate, the water should weigh between 24.9252g.
3
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