scenario
You are a newly appointed technical assistant at a large chemical plant, Chemcalequip. As part of your induction period and to progress in your role, you must demonstrate skills in a range of practical procedures and techniques. Part of your role is to ensure equipment is calibrated and e...
Unit 2 – practical scientific procedures + techniques
Learning aim, A – undertake titration + colorimetry to determine the concentration of solutions.
scenario
You are a newly appointed technical assistant at a large chemical plant, Chemcalequip. As part of your
induction period and to progress in your role, you must demonstrate skills in a range of practical
procedures and techniques. Part of your role is to ensure equipment is calibrated and equipment and
chemicals are safety checked. A key part of your job will be making and testing standard solutions using
calorimetry and titration. You must demonstrate your ability to carry out these techniques. Evidence of
your practical skills, along with your results, calculations, evaluation of the techniques and possible
improvements will need to be submitted in a report.
Density of water at 21C - 0.997992g/cm3 or 997.992kg/m3and the room temperature was 23, 19, 21.
The average room temperature – 21C.
The three experiments must always be performed with calibrated equipment. Weighing scales, pippete,
burettes, and the pH metre that will be needed are the pieces of equipment that require calibration.
How to calibrate a burette
Fill a clean, dry burette with 50ml of distilled water.
Allow the suspended drop to drop while the meniscus is slightly below zero.
Take a clean and dry beaker and weigh it on a weighing scale set to zero.
Fill the beaker with 10ml of the distilled water from the burette. Allow some time for water to drain
from the burette's walls.
To determine how much water was dropped from the burette, weigh the beaker on the zeroed weighing
scales.
Subtract the difference between the level at which the burette dropped and what was dropped to get
the measurement correction.
How to calibrate (top pan weighing scale)
Place a weighing scale on a flat surface.
Turn on the weighing scale and set it to zero.
Place a calibrated weight, such as a small weight that has been measured to be accurate, on the scale.
, Weight should be adjusted until it displays the correct weight.
How to calibrate a ph metre
Items needed to calibrate a ph metre;
Distilled water
· pH meter
· pH7 buffer solution
· pH10 buffer solution
· Beaker (150ml)
· Safety goggle
When calibrating a pH metre, you must use different pH buffer solutions; for our pH metre, the buffer
solutions used were pH 7 and pH 10. We calibrated the pH metre using pH 7 first. When calibrating the
pH metre with buffer 7, place the pH metre in the solution and press the cal (calibrate) button on the pH
metre. If your pH metre reads 7 or higher, it has been properly calibrated. Following that, we used
distilled water to rise to the end of the pH metre to ensure that there was no access pH 7 buffer on the
pH stick. After that, we repeated the process with the pH 10.
Finding the concentration of sodium hydroxide
To determine the concentration of an unknown sodium hydroxide solution, perform the experiments in
this article (NaOH). To do this, prepare a standardised sodium carbonate solution (Na2CO3) and titrate it
against a hydrochloric acid solution with an unknown concentration (HCl). This experiment should make
it able to determine the hydrochloric acid concentration. It is feasible to determine the concentration of
the unidentified Sodium Hydroxide (NaOH) using the experiment's determined hydrochloric acid
concentration. Burettes and pipettes will be utilised during the tests. When compared to measuring
cylinders, these are more precise. This is as a result of the error margin. On a measuring cylinder, the
margin of error is typically 0.5. A Burette's margin of error is frequently 0.05. A pipette's margin of error
is typically 0.01. This is because the pipette and burette are specifically designed to accurately measure
liquids.
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