pH, BUFFERS AND ISOTONIC SOLUTIONS Sele£ted Dellnitions •
pH of the solution is defmed as the negative logarithm of the hydrogen ion concentration.
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ButTers are compounds or mixtures of compounds which, due to their presence in solution, resist changes in
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ButTer Action: It is defined as the resistance to a change in pH.
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ButTer Solution:
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Acidic butTer solution is the solution whose pH is less than 7.
pH after addition of small amounts of acid or alkali. A solution whose pH is not much altered by the addition of small amounts of strong acid (H
+ ions) or a strong base (OH- ions). •
Alkaline butTer solution is the solution whose pH greater than 7.
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ButTer Equation:
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ButTer Capacity:
This equation is used to calculate the pH of a buffer solution and the change in pH with the
addition of an acid or base. It is the measure of its magnitude of its resistance to change in pH in the addition of an
acid or a base. •
Maximum butTer capacity: This occur when pH = pKa
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Osmosis:
The movement of water molecules across a semi permeable membrane from region of low solute
concentration to high solute concentration. •
Isoosmotic solutions: The solutions having same osmotic pressure as blood.
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Isotonic solution:
The solution having the same salt concentration and hence the same osmotic pressure as
the red blood cell. •
Hypertonic
solutions: The solution having an osmotic pressure greater than that of O.9%w/v sodium chloride.
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Hypotonic solutions: The solutions having an osmotic pressure lower than that of O.9%w/v sodium chloride.
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Osmolality:
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Osmolarity:
It is the number of os moles of solute in a kilogram of solvent.
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Tonicity-
It is the number of osmoles of solute in a litre of solution.
It is the concentration of only the solutes that cannot cross the membrane since these solutes exert
an osmotic pressure on that membrane.