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In simpler terms, osmolality is an expression of solute osmotic concentration per mass of solvent, whereas osmolarity is per volume of solution (thus the conversion by multiplying with the mass density of solvent in solution (kg solvent/litre solution). =
Whereas osmolality (with an "l") is defined as the number of osmoles (Osm) of solute per kilogram of solvent (osmol/kg or Osm/kg), osmolarity (with an "r") is defined as the number of osmoles of solute per liter (L) of solution (osmol/L or Osm/L). As such, larger numbers indicate a greater concentration of solutes in the plasma.
For liquid solutions, the osmotic coefficient is often used to calculate the salt activity coefficient from the solvent activity, or vice versa. For example, freezing point depression measurements, or measurements of deviations from ideality for other colligative properties, allows calculation of the salt activity coefficient through the osmotic coefficient.
The osmol gap is typically calculated with the following formula (all values in mmol/L): = = ([+] + [] + []) In non-SI laboratory units: Calculated osmolality = 2 x [Na mmol/L] + [glucose mg/dL] / 18 + [BUN mg/dL] / 2.8 + [ethanol/3.7] [3] (note: the values 18 and 2.8 convert mg/dL into mmol/L; the molecular weight of ethanol is 46, but empiric data shows that it does not act as an ideal ...
[2] 290 mOsm/kg is the presumed stool osmolality, and the measured concentration of sodium and potassium cations is doubled to account for the corresponding anions which must be present. [citation needed] A normal gap is between 50 and 100 mOsm/kg, [3] corresponding to the concentration of other solutes such as magnesium salts and sugars ...
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
Urine osmolality in humans can range from approximately 50 to 1200 mOsm/kg, depending on whether the person has recently drunk a large quantity of water (the lower number) or has gone without water for a long time (the higher number). [2] Plasma osmolality with typical fluid intake often averages approximately 290 mOsm/kg H 2 O in humans. [2]
The molar mass of atoms of an element is given by the relative atomic mass of the element multiplied by the molar mass constant, M u ≈ 1.000 000 × 10 −3 kg/mol ≈ 1 g/mol. For normal samples from Earth with typical isotope composition, the atomic weight can be approximated by the standard atomic weight [ 2 ] or the conventional atomic weight.