Of a solute in solutionAmount of substanceDivided by solventquality, is called the mass molar concentration of the solute (mol/kg).In very dilute aqueous solution, it can be approximately considered thatAmount and concentration of substanceIs numerically equal to the molar mass concentration.This is because when the aqueous solution is very dilute, the mass of solute can be ignored, the volume of solution can be considered as the same as the volume of water, the density is 1kg/L, the mass of solvent water is approximately equal to the mass of solution, and numerically equal to the volume of solutionV(L)。[1]
Molar mass concentration of solute B, the symbol is bBOr b (B), which is defined as the amount of solute B in the solution
Divided by the mass of solvent A, the mathematical expression is[2]：
Where, SI unit of mass molar concentration is mol · kg-1Or mol/kg.(Molar mass concentration is recorded asmB, pay attention to subscripts, but in order to avoidmSymbol confusion, usingbFor easy understanding.)
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(1) Quality
It refers to the quality of solvent rather than the quality of solution.
(2) Molar concentration refers to the amount concentration solution of the substance, not the mass molar concentration.
(3) Solute B can be a simple substance, a compound, or a specific combination of ions or other complex ions.
For example: b (Cltwo）=0.1mol·kg-1、b(NaCl)=2.0mol·kg-1、 b(Fe2+)=0.5mol·kg-1Etc.[3]
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Since the mass molar concentration of solute B is independent of temperature, the volume of solvent in the mass concentration of substance may be affected by temperature.Therefore, the mass molar concentration is mostly used in thermodynamic treatment, and the mass molar concentration is also mainly used in electrochemistry to represent the concentration of electrolyte.However, when the solvent is a dilute solution of water, that is, bB<0.100mol·kg-1，bBAndcBThe values of are approximately equal.[1]
