Home » articles » CKD-ESKD » Numbers-Their Use and Interpretation » Concentration, atom Weight and also Molarity, and Avogadro’s Law


The units of measurement of an lot of substance space conveniently reported together concentration i m sorry is mass per unit of volume. The unit of volume favored is typically one ideal to the expected concentration that the substance or to a volume that renders physiological sense – gram / liter (g/l), millimole / liter (mmol/l), milligram / milliliter (mg/ml).

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If we recognize the concentration that a substance (mass/volume) and we recognize the total volume that solvent in which the problem (solute) is liquified (volume), it follows that the full mass the solute is offered byconcentration (mass/volume) x total volume = complete mass

Similarly, knowing full mass and also concentration gives total volume the solvent astotal mass/concentration (mass/volume) = complete volume

And, given complete mass and also total volume gives a result for concentration astotal mass/total volume = concentration

Atomic weight and also molarity

The atomic weight of a substance is one assigned number which allows comparison that the family member masses (weights) the the various elements. By definition, one atom that oxygen is assigned a “weight” of 16, and also the atomic weights that the other aspects are established in relation to that of oxygen. In a molecule, i.e., a problem containing 2 or much more different atoms, the molecular weight is equal to the sum of the atom weights of the individual atoms. Because that example, the molecular weight of water (H2O) is 18 (<2 x 1> + 16).

One mole (mol) of any substance is identified as the molecule (or atomic) load of the substance in grams. Similarly, one millimole (mmol) is same to one-thousandth the a mole or the molecule (or atomic) weight in milligrams.

The atomic load of salt (Na+ ) is 23. Therefore, for Na+,

23 g = 1 mole

23 mg = 1 mmol

23 mg the Na+ in 1 liter that water = Na+ concentration () the 1 mmol/l.

Avogadro’s Law

Avogadro’s regulation states that 1 mole of any non-dissociable substance (a substance than cannot be further diminished to component units) includes the same variety of particles (approximately 6.02 x 1023 = Avogadro’s number).

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Thus, 1 mmol that Na+ has the same number of atoms together 1 mmol that Cl- even though the previous weighs 23 mg and the latter weighs 35.5 mg. However, 1 mmol the NaCl (58.5 mg) largely dissociates right into Na+ and Cl- ions and also therefore contains practically twice as many particles.

The concentration the uncharged molecules, e.g., glucose and urea, additionally can it is in measured in millimoles every liter and this is frequently the situation where the Systeme international (SI units) is used. However, elsewhere, they are much more commonly measured in the clinical laboratory together milligrams per deciliter (mg/dl or mg%). The molecular load (mol wt) the glucose is 180. Consequently, a glucose concentration that 180 mg/l (or 18 mg/dl) is same to 1 mmol/l. To transform from milligrams per deciliter to millimoles every liter, the adhering to formula deserve to be used: