Pharmacy math tutoring exam 6 Jillian Schmidt jschmi24@uthsc.edu

Chapter 12: Electrolyte solutions: milliequivalents, millimoles, milliosmoles Objectives: Calculate the millimoles from atomic or formula weight Convert between milligrams and millimoles Calculate the milliequivalents from atomic or formula weight Convert between milligrams and milliequivalents Convert between millimoles and milliequivalents

Millimoles One mole : molecular weight in grams One millimole : molecular weight in milligrams

Osmolarity Unit used to measure osmotic concentration Millimoles of solute per liter of solution Nonelectrolytes Compounds that do not dissociate in solution Each 1 mmol contributes 1 mOsmol Electrolytes Separate into ions Each 1 mmol contributes 2 mOsmol (one from each ion) mOsmol/L = (wt of substance in g/L / MW in g) * number of species * 1000

milliequivalent Used to express the concentration of electrolytes in solution Relates to the total number of ionic charges in solution Determine the moles or millimoles and multiply by the valence Valence- amount of charge of an ion Equivalents (Eq) The number of univalent counter ions needed to react with each molecule of a substance Example: HCl has 1 equivalent per mole, 1 mole of H+ reacts with one mole of Cl- For a given compound, the mEq of cations equals the mEq of anions

milliequivalents mEq represents the amount of a compound in milligrams equal to 1/1000 of its molecular weight taking into account the valence of the ions mEq = (mg x valence) / (molecular weight)

0.9% NaCl 9g/1000mL 9000 mg/L mEq? (9000mg/L)/58.5mg/mmol= 154mmol/L*1mEq/mmol= 154mEq/L *1L/1000mL= 58.5 g/mol *1000mg/g * 1mol/1000mmol 58.5 mg/mmol

2 mEq/ml KCl Mg? 2mEq/mL * 1mmol/1mEq= 2mmol/mL 2mmol/mL*74.5mg/1mmol= 149mg/mL