Unit 2- Practical Scientific Procedures and Techniques
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Unit 2
Assignment A
Diana Duka
Titration
Aims
The main purpose of the experiments are to find the concentrations of the chemicals used,
for example hydrochloric acid.The objective of these experiments are to test the end point
while the reaction occurs. Altogether, there will be three different practicals with three
different objectives. Some will have an exothermic reaction, where heat is given out to the
surroundings. Also, during the experiments there will be lots of observations made, this
including the change in colour when the indicator is added to the solution and the colour
change when the hydrochloric acid is added to the solution to create a titre. In the following
report, I will be discussing the different types of titrations and their uses, the safety of
chemicals used during the experiment, risk assessments completed before the experiments,
I will be describing the way I did my experiment as well as analysing the results I obtained.
Introduction
Titration is the process used to determine the volume of solution that is either acidic or alkali
in order to neutralise the solution provided. Before doing the experiment, the preparation of a
standard solution is required, which you will know the concentration and volume of. This is
called the ‘titrant’. Another solution, called the ‘analyte’ is used until the endpoint is met. This
is the point where there is an equivalent volume of both solutions. During titration, a small
amount of analyte is added to a conical flask with a few drops of indicator and is then placed
under a calibrated burette containing the titrant. Titration is mainly used in chemistry to
determine the concentration of a solution. There are several different types of titration; acid-
base titration, redox and precipitation titration. The different types of titration have different
purposes and outcomes. For example acid-base titration is used for a quantitative analysis
of a known concentration which neutralises the unknown concentration of a given solution.
Redox titration is used to determine the concentration of an oxidising/ reducing agent and
last but not least, precipitate titration is used to measure the precipitate formed during the
titration. I will be going into more detail to describe the purpose and uses of the three main
titration methods.
Solution - a homogeneous mixture of substances.
Accuracy - the degree to which the result conforms to the correct value. (1.)
Precision - the closeness of two or more measurements to each other. (2.)
Reliability - experimental results that are repeated under the same conditions and get very
close/similar results.
,Titrant - a solution of which you know the concentration
Calibration of electric balance
Why should you calibrate the equipment before use?
It is essential to calibrate the apparatus before using it in an experiment because it can affect
the results. The results can be less accurate, less precise and less reliable for others to use
the results. Calibrating the equipment before an experiment can show the ageing of the
equipment and any problems it may have, so there is time to resolve any issues with
apparatus for a more precise and accurate quantitative result analysis. Also, the calibration
of laboratory equipment is mandatory because the reliability of the equipment decreases as
time goes on, which will alter the accuracy of the results.
How to calibrate the electronic balance
Place the balance onto a flat surface. Press ON and wait for 2-3 mins.The display should
show 0.00g. Then press the CAL key and wait till the display shows ‘C’, internal calibration
should be in progress. After, the display should turn back to showing 0.00g. This means
balance has been successfully calibrated.
[Figure 3 - calibration of digital scale]
Calibration of a pH metre
Equipment needed for calibration of pH metre
● 100ml beaker
● pH metre with sample solution provided, screwdriver in kit
● Distilled water
○ How to calibrate the pH metre
Switch on pH metreRemove protection cap and pull out electrode Take a 100ml
beaker and pour approx. 50ml of distilled water.Dip electrode into the distilled water
and wipe dry.Get sample solution (pH value of 7.0), unscrew cap and dip electrode
into solution. Stir electrode and wait till the display stabilises.Adjust the reading on
, the pH metre by turning the trimmer on the side, with the screwdriver provided to
7.0.After calibration, rinse the electrode in the distilled water and wipe dryDip the
electrode into the sample solution, wait until stable reading is obtained. Remove from
the sample solution and dip into distilled water, wipe dry.Place protection cap back
onto the electrode. Calibration is complete.
○ Is the buffer solution safe?
Yes, reports show there are no side effects, it is not toxic or carcinogenic.
One thing to note, if you come into contact with a buffer solution, wash your
hands with panty of water or rinse your eyes. “The product is not classified as
hazardous according to Regulation (EC) 1272/2008 as amended.” (2.)
[Figure 2 - calibration of pH meter]
Risk Assessment
Hazard Risk Precaution
Buffer solution May get into eyes Wear eye protection and
take care when around
solution
Types of titration and their uses
○ Acid-Base Titration - is a quantitative analysis of acid and bases where a
known concentration neutralises an unknown concentration of a solution. This
method of titration is also known as ‘Acidimetry’ or ‘Alkalimetry’. Acidimetry is
when an acidic solution is reacted with a strong base of standard solution.
Acids are classified as strong or weak depending on the amount of H⁺ ions
dissociating.
○ Redox Titration - reaction between an oxidising and a reducing agent. This
titration focuses on the concentration of the reducing agent or oxidising agent.
During the titration, one of the agents acts as self indicators. It requires
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