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Title: Dilutions and Titrations
Description: This is an overview on the reasons for, and processes involved with dilutions and titrations of chemicals
Description: This is an overview on the reasons for, and processes involved with dilutions and titrations of chemicals
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Module: BIOM - 1007
Lecturer: Dr Weldon
Date: 28/10/16
Dilutions and Titrations
o
Sometimes you know the concentration of a solution but it’s not what you require
Therefore, you must dilute the stock solution
The amount of substance (mol) is the same in the diluted sample as the undiluted
sample
The volume is the only variable that changes
o
To dilute a sample, take the volume of the original solution and add a known volume of solvent to
produce a more dilute solution
The undiluted and diluted sample has the following equations respectively:
Moles = C1 x V1
Moles = C2 x V2
Therefore: C1V1 = C2V2
o
For example, if you have 100ml of a 2M HCL solution and you add 900ml of H2O, what is the concentration
of the diluted sample?
It will be 0
...
2/1 = c
C = 0
...
2L and the concentration of the
diluted solution is 0
...
2x2)/0
...
This is then repeated and yields many different sample dilutions
o
Titration is used to directly measure the concentration of a sample
This is done using a series of chemical reactions to measure amounts in a sample
The production of a product is key in this process
A burette is used to deliver the second reactant to a flask and an indicator is used to
detect the endpoint of the reaction
o
A coupled reaction is when the product from one reaction is then used straight way as the ingredient for
another reaction, for instance A+B=C and C+D=E, therefore you cannot get E without A or B
o
UV spectroscopy can be used to detect the concentration of a sample:
The amount of light that passes through the sample is indirectly proportional to the
concentration
In a low concentration, much light passes through the sample
In a high concentration, little light passes through
The Beer-Lambert law states that the absorbance of light is equal to the molar absorptivity (L
mol-1 cm-1) (ε) x the concentration (mol L-1) (c) x the path length (cm) (l):
� = ���
Title: Dilutions and Titrations
Description: This is an overview on the reasons for, and processes involved with dilutions and titrations of chemicals
Description: This is an overview on the reasons for, and processes involved with dilutions and titrations of chemicals