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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] A standard solution ideally has a high degree of purity and is stable enough that the concentration can be accurately measured after a long shelf time. [2]
The standard state molality is 1 mol/kg, while the standard state molarity is 1 mol/dm 3. Other choices are possible. For example, the use of a standard state concentration of 10 −7 mol/L for the hydrogen ion in a real, aqueous solution is common in the field of biochemistry.
Making a saline water solution by dissolving table salt in water.The salt is the solute and the water the solvent. In chemistry, a solution is defined by IUPAC as "A liquid or solid phase containing more than one substance, when for convenience one (or more) substance, which is called the solvent, is treated differently from the other substances, which are called solutes.
For example, if there are 10 grams of salt (the solute) dissolved in 1 litre of water (the solvent), this solution has a certain salt concentration . If one adds 1 litre of water to this solution, the salt concentration is reduced. The diluted solution still contains 10 grams of salt (0.171 moles of NaCl).
A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are used to calibrate other standards referred to as working standards. [1] [2] See Hierarchy of Standards.
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Here, is the amount of the solute in moles, [4] is the number of constituent particles present in volume (in litres) of the solution, and is the Avogadro constant, since 2019 defined as exactly 6.022 140 76 × 10 23 mol −1.
The first step (called SC-1, where SC stands for Standard Clean) is performed with a solution of (ratios may vary) [2] 5 parts of deionized water; 1 part of ammonia water, (29% by weight of NH 3) 1 part of aqueous H 2 O 2 (hydrogen peroxide, 30%) at 75 or 80 °C [1] typically for 10 minutes. This base-peroxide mixture removes organic residues.