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A measurement system can be accurate but not precise, precise but not accurate, neither, or both. For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy. The result would be a consistent yet inaccurate string of results from the flawed experiment.
Accurate structural parameters and vibrational frequencies are a natural byproduct of the method. While the computed molecular properties can be highly accurate, the computationally intensive nature of the FPD approach limits the size of the chemical system to which it can be applied to roughly 10 or fewer first/second row atoms.
Because of the complex inter-relationship between analytical method, sample concentration, limits of detection and method precision, the management of Analytical Quality Control is undertaken using a statistical approach to determine whether the results obtained lie within an acceptable statistical envelope.
Chemical accuracy is the accuracy required to make realistic chemical predictions and is generally considered to be 1 kcal/mol or 4 kJ/mol. To reach that accuracy in an economic way, it is necessary to use a series of post-Hartree–Fock methods and combine the results. These methods are called quantum chemistry composite methods. [56]
Examples of the exact sciences are mathematics, optics, astronomy, [3] and physics, which many philosophers from Descartes, Leibniz, and Kant to the logical positivists took as paradigms of rational and objective knowledge. [4] These sciences have been practiced in many cultures from antiquity [5] [6] to modern times.
In analytical chemistry, a standard solution (titrant or titrator) is a solution containing an accurately known concentration.Standard solutions are generally prepared by dissolving a solute of known mass into a solvent to a precise volume, or by diluting a solution of known concentration with more solvent. [1]
Because 6 mole of fluoride react with one mole of aluminium, the titration is particularly precise, and a coefficient of variance (CV) of 0.03 has been achieved in the analysis of alum. When aluminium ion (say as aluminium nitrate) is employed as the titrant, fluoride can be determined using the same chemistry.
The SMARTS line notation is expressive and allows extremely precise and transparent substructural specification and atom typing. SMARTS is related to the SMILES line notation that is used to encode molecular structures and like SMILES was originally developed by David Weininger and colleagues at The Pomona College Medicinal Chemistry Project ...