Solutions
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solution |
- homogenous mixture formed by the dispersion
of a gaseous, liquid or solid substance [solute] within a liquid [solvent] |
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Types of Solutions |
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crystalloid solution |
- the solute particles are of such a size
& nature to become equally dispersed in the solvent by Brownian motion —
will remain homogeneously dispersed despite gravity. - include small ions, simple acids/bases,
small organic molecules (glucose), small nitrogenous molecules (urea). - upper limit 50K — 100K Daltons - not restricted by biological membranes |
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colloidal solution |
the solute particles will be subjected to
gravity [of extreme time duration] thus resulting in the solution losing its
homogeneity. - lower limit 40K — 50K Daltons - restricted by biological membranes |
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suspension |
the solute particles will be subjected to
gravity [once mixing or stirring has ceased] thus resulting in the solution
losing its homogeneity. - eg well mixed blood |
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Descriptions of Concentrations of
Solute in Solvent |
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Volume per
100 volumes |
- eg Hct of 40% — for every 100 mls blood, the
cells occupy 40 mls - eg concentration of O2 in
arterial blood is 20 vol% — for every 100 ml blood, 20 ml of O2 therein
dissolved |
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Weight per
100 weights |
- most accurate concentration designation - not affected by temperature - not used in medicine |
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Weight per
100 volumes |
- eg 15 gm% Hb concentration — 15 gm Hb per
100 mls blood - is preferable to use 15 gm/dl blood |
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Descriptions of Concentrations of
Solute in Solvent in terms of chemical or physical activity |
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mole |
- molecular weight of a substance in grams [gm
molecular weight] - 6.25 x 1018 atoms,
ions, molecules |
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molar |
- weight per volume concentration - ie 1 molar solution contains 1 mole of the
specified solute per 1000 mls solution - eg 180 gm dextrose made up to 1 L — 1 molar
concentration of dextrose - eg 58.5 gm NaCl [ Na=23 + Cl=35.5]
in 1 L solution — 1 molar concentration |
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molal |
- a weight per weight designation - ie 1 molal solution contains 1 mole of the
specified solute per 1000 gms solution - less used in medicine |
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equivalents |
- gram-equivalent weight of a substance is
that weight of a substance that will react with 1 mole [1.008 gm] H+ - eg 1 mole (58.5 gm) NaCl in 1 L solution [ie
a 1 molar concentration]; as have 1 mole Na + 1 mole Cl and both Na & Cl
have valencies of 1, the Na in this 1 molar solution is equivalent to 1 mole
of hydrogen & ditto for Cl — the concentration of Na+
(& Cl-) is one equivalent per litre - eg 1 mole (111 gm) CaCl2 in 1 L solution [ie a 1 molar
concentration]; as have 1 mole Ca + 2 mole Cl and as Ca has a valency of 2
& Cl a valency of 1, the Ca in this 1 molar solution is equivalent to 2
mole of hydrogen & ditto for Cl — the concentration of Ca2+
(& Cl-) is two equivalents per litre |
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normality |
- a normal
solution has 1 gm equivalent weight [1 mole] of solute in 1 L of solution - another means of expressing equivalents - not used in medicine |
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Descriptions of Concentrations of
Solute in Solvent in terms of total number of particles disregarding chemical
activity of the individual particles |
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osmole |
- the unit of osmolarity - 6.25 x 1018
particles per 1000 ml fluid - eg 1 mole dextrose in 1L —> 1 osmole/L - eg 1 mole NaCl in 1L —> 2 osmole/L - eg 1 mole CaCl2
in 1L —> 3 osmole/L - eg 1 osmole/L solution CaCl2
—> 1/3 mole or 111/3 =
37 gm |
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osmosis |
- movement of a solvent [water] through a
semipermeable [permeable only to the solvent] membrane from an area of low
solute concentration to an area of high solute concentration |
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osmotic
pressure |
- pressure required to stop osmosis - cmH20 or mmHg |
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tonicity |
- a relative term comparing osmotic pressure
exerted by various solutions - eg pure water is hypotonic relative to red
cell [.307 osmoles] |