Test 4: Solutions Lecture 3 Biological Concentrations Flashcards
Two concentration units which are commonly used for biological concentrations
Equivalents and osmolarity
Equivalents are used in solutions where
we are interested only in one ion
Equivalents are measured in
Eq, or milliequivalents, mEq (1/1000th of an equivalent, of
course) over volume
One equivalent is defined as one mole of
(+) or (-) charges.
Mathematical expression of equivalents
Equivalents = moles*charge(of the ion)
When working with mass amounts, to calculate the amount of one equivalent of an ion, take the
molar mass of the ion and divide it by the total
charge of the ion (1 Eq=mass/charge) absolute value, so drop the negative
If comparing initial to final, units must be
The same, but not a specific unit
If using a formula that is not comparing initial to final conditions, must use units __
defined for that system
1 Eq (ion) = 1 mole (ion) / charge of ion
Steps to calculate osmolarity
First calculate the molarity, then multiply by the total number of species dissociating when the compound is dissolved in water.
If the compound is covalent, it will not dissociate, so the osmolarity is __ when determining particles.
the same as the molarity
Molarity (M) = moles of solute * PARTICLES/Liters of solution
Osmolarity (osmol) = moles (M) * particles
If the compound is ionic and soluble, you must count the total number of__to get the particles.
ions present in the formula
Colligative properties
Physical properties that change with the presence of solute particles.
