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Unit 19 - Practical Chemical Analysis Assignment 1 (Full)
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Assignment 1Unit 19 - Chemistry
During practical chemistry analysis quantitative analysis is typically used. Quantitative tests are
known as any methods which can be used to determine the amount (quantity) of a chemical within a
sample, through expressing the amount using numbers of
appropriate units. Chemical methods are dependent upon reactions
like oxidation, neutralisation, precipitation, etc. The main tool for
quantitative tests is a scale or analytical balance, this allows a mass
of a sample to be measured as accurately as possible. The chemical
methods used during quantitative test will have a chemical reaction.
Some chemical methods are; Titration, combustion tests, etc.
Titration is known as the slow addition of one known concentration
solution (titrant) to a known volume of another solution which has
an unknown concentration, the addition will continue until the
reaction reaches neutralisation. Neutralisation is often indicated
through the observation of a colour change. Titration often involves a
burette; a burette is known as a graduated glass tube which has a tap
at one end and is primarily known for delivering volumes of liquids.
Over the period of two weeks (11/10/19 – 18/10/19) Level 3 BTEC Applied Science (Forensic Science)
Group B students, individually under test-conditions carried out two separate chemistry practicals
regarding standardisations, involving different chemicals in the attempt to establish an unknown
concentration of a chemical. The first practical I carried out was the Standardisation of a Sodium
Hydroxide Solution using Succinic Acid.
Standardisation of a Sodium Hydroxide Solution using Succinic Acid.
Aim
For the best possible outcome to be achieved from this standardisation there are some aims which
need to be conducted, these are; for a standard solution to be prepared, a standardisation of an
acceptable degree of accuracy must be performed, for the Sodium Hydroxide solution concentration
to be calculated, and finally the possible sources of error must be commented on and an evaluation
on the answer which has been obtained.
Introduction
Succinic Acid (CH2COOH)2 is a dibasic acid. The term dibasic means that within each molecule there
are two acidic hydrogens. This acid naturally occurs in plant and animal tissues. Succinic acid is able
to be used as a primary standard for standardising solutions of alkali. A Sodium Hydroxide solution is
more dense in comparison to water and appears as a liquid which is colourless. Succinic Acid reacts
with Sodium Hydroxide as follows;
As Succinic Acid is a primary standard it’s able to be
COOH COO -Na+ used to standardise a Sodium Hydroxide solution.
During this experiment, a Succinic Acid solution of a
CH2 CH2 suitable concentration (the Succinic Acids
+ 2NaOh + 2H 2O concentration is known, Sodium Hydroxide
CH2 CH2 concentration is unknown – this is what we were
COOH COO -Na+ finding, the concentration of Sodium Hydroxide)
needed to be prepared for a Sodium Hydroxide
Safety & Hazards solution to be standardised.
To ensure an individual is safe throughout this
practical there are control measures which have been sternly put in place and must be followed,
these control measures are as follows;
A laboratory coat and safety goggles is mandatory to be worn by an individual during this
practical, to ensure no hazardous substances come into contact with the skin. A laboratory
1
, Assignment 1
Unit 19 - Chemistry
coat and safety goggles also are sufficient enough to take account of the most hazards as
well as risks deemed significant.
It’s important that immediately after use waste is placed in labelled containers, where waste
can then be correctly disposed of by a scientific technician.
A good laboratory practice is remined of in order for a safe working environment to be
maintained.
Highly Flammable = Phenolphthalein.
Corrosive = Sodium Hydroxide Solution.
Harmful! Irritant = Succinic Acid.
Method
1. Firstly, accurately weigh out between 1.4 and 1.5g of succinic acid to 3 decimal places, do
this by using the ‘weighing by difference’ method. The obtained mass reading must be
recorded.
2. Next, the Succinic Acid must be placed into a small beaker before 30-40cm 3 of deionised
must be added. This acid must be dissolved through carefully stirring it, ensuring none is
spilt.
3. Thirdly, once the acid has been dissolved the solution needs to be transferred to a 250.0cm 3
volumetric flask. It must be ensured that the beaker is washed out with deionised water
numerous times as this will ensure that all the acid has been transferred. Now make up the
mark by adding deionised water.
4. After that, 25cm3 of Succinic Acid solution needs to be pipetted into a conical flask, before
adding 3-4 drops of phenolphthalein indicator, and titrate this with the given sodium
hydroxide solution. Near the endpoint the Sodium Hydroxide will need to be added
dropwise and the mixture swirled. Once there is a permanent pink tinge the titre can be
recorded.
5. Finally, repeat the titration until three consistent titres have been obtained.
Results
1.) Find the accurate mass of succinic acid.
Mass = mol x molar mass (mr).
Mass = 1.48g ( This is the mass which was obtained through the weighing by
difference method.)
2.) Calculate the moles of succinic acid.
Moles = mass(g) ÷ molar mass (mr).
Carbon (C) = 12 , Oxygen (O) x 2 = 16 x 2 , Hydrogen (H)= 1.01 , Carbon (C) = 12,
Hydrogen (H) x 2 = 1.01 x 2 , Carbon (C) = 12, Hydrogen (H) x 2 = 1.01 x 2 , Carbon (C)
= 12 , Oxygen (O) x 2 = 16 x 2 , Hydrogen (H) = 1.01
mr = 12 + (16 x 2) + 1.01 + 12 + (1.01 x 2) + 12 + (1.01 x 2) + 12 + (16 x 2) + 1.01 =
118.06mr.
1.48g ÷ 118.06 = 0.0125mol.
0.0125mol ÷ 10 = 0.00125.
3.) Calculate the concentration of acid in 250cm3.
2
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