This assignment is the first of unit 19 - Practical Chemical Analysis, with the title of 'Analyte determination', learning aim A: Investigate quantitative analysis on the components of matrices to determine their composition. This is a high-quality assignment, with extremely in-depth information an...
A: Investigate quantitative analysis on the components of matrices to
determine their composition
, Experiment 1: The percentage of copper in brass (by reacting with
acid and using colorimetry)
M2: Compare the use of primary and secondary titrimetric standards
Primary and secondary standard solutions are crucial in quantitative analysis, particularly for
titrations, to ensure accurate and precise measurements. In order to compare their uses, it is
necessary to first define both primary and secondary standards, explain the standardization
process involving these solutions, and discuss the choice of secondary standards over primary
standards in the context of the given experiment.
Primary standard solutions are solutions containing a known concentration of a highly pure and
stable substance that do not significantly change over time when stored properly. They meet
specific criteria, such as high purity, a known stoichiometry for reactions, stable composition,
and low reactivity with the environment. Examples of primary standards include potassium
hydrogen phthalate (KHP) for pH determination and anhydrous sodium carbonate (Na2CO3) for
acid-base titrations.
Secondary standard solutions, on the other hand, are solutions with a known concentration but
that don't meet all the criteria for primary standards. These solutions may be less stable, have
lower purity, or exhibit hygroscopic properties. Therefore, to ensure accuracy, secondary
standard solutions must be standardized against primary standard solutions before use.
Standardization refers to the process of determining the concentration of a secondary standard
solution by titrating it against a primary standard solution, using their known stoichiometry.
Standardization is the process of determining the accurate concentration of a secondary
standard solution by titrating it against a primary standard solution with a known concentration.
This process allows for the precise calculation of the secondary standard's concentration, thus
ensuring confidence in subsequent analytical measurements. During titration, both the primary
and secondary standard solutions' volumes are carefully measured and compared. By utilizing
the stoichiometry of the reaction between the primary and secondary standards and considering
the known concentration of the primary standard, the exact concentration of the secondary
standard solution can be calculated.
In the context of the specific titrimetric work for determining the percentage of copper in brass
using acid reactions and calorimetry, the use of secondary standards is chosen over primary
standards for several reasons:
1. Availability: Secondary standard solutions can often be prepared from more readily
available laboratory reagents, which can then be standardized against primary
standards.
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