Quantity and Concentration Expression. Expressions of Quantity of Drugs One molecule of a substance...

Quantity Quantity and and

Concentration Concentration ExpressionExpression

Expressions of Quantity of DrugsExpressions of Quantity of Drugs

One One moleculemolecule of a substance is too small a quantity to be of a substance is too small a quantity to be pharmaceutically useful. It is convenient to measure in a larger pharmaceutically useful. It is convenient to measure in a larger unit. Usually the unit used for this purpose is the unit. Usually the unit used for this purpose is the molemole (abbreviated mol), which is Avogadro’s number (6.023 X 1023) (abbreviated mol), which is Avogadro’s number (6.023 X 1023) of molecules. of molecules.

The The molecular weightmolecular weight (MW) of a compound is the weight in (MW) of a compound is the weight in grams of one mole of the compound. grams of one mole of the compound.

MillimolesMillimoles (mmol) often are used in pharmacy rather than (mmol) often are used in pharmacy rather than moles because the required quantities and concentrations of moles because the required quantities and concentrations of drugs are relatively small. drugs are relatively small.


The The equivalent weightequivalent weight of an element or compound of an element or compound is that weight which combines chemically with one is that weight which combines chemically with one equivalent of another element or compound equivalent of another element or compound

Equivalent weightEquivalent weight = Atomic or Molecular Weight = Atomic or Molecular Weight Number of Equivalents per Atomic Number of Equivalents per Atomic or or Molecular Weight Molecular Weight ( valence)( valence)

MilliequivalentsMilliequivalents (mEq) are used often in pharmacy because, when (mEq) are used often in pharmacy because, when dosing electrolytes, we are usually dealing with small quantities.dosing electrolytes, we are usually dealing with small quantities.

Expressions of Quantity of DrugsExpressions of Quantity of Drugs Example Calculation 1Example Calculation 1

You have a formula that calls for 0.5 moles of Sodium You have a formula that calls for 0.5 moles of Sodium Hydroxide (NaOH). Sodium Hydroxide is available as a Hydroxide (NaOH). Sodium Hydroxide is available as a solid. How many grams of NaOH should you weigh? (MW solid. How many grams of NaOH should you weigh? (MW of NaOH = 40)of NaOH = 40)

1 mole of NaOH 40 g1 mole of NaOH 40 g 0.5 mole of NaOH x g0.5 mole of NaOH x g

x = 0.5 x 40 = 20 gx = 0.5 x 40 = 20 g1


You have a liquid formulation that has 600 mg You have a liquid formulation that has 600 mg of Potassium Chloride (KCl) in each of Potassium Chloride (KCl) in each teaspoonful of syrup. How many millimoles teaspoonful of syrup. How many millimoles of KCl this would be? (MW of KCl = 74.5)of KCl this would be? (MW of KCl = 74.5)

Example Calculation 3Example Calculation 3

A potassium supplement tablet contains 10 A potassium supplement tablet contains 10 mEq of KCl. How many milligrams of KCl mEq of KCl. How many milligrams of KCl are in each tablet? (MW of KCl = 74.5)are in each tablet? (MW of KCl = 74.5)

1 mEq of KCl 74.5 mg1 mEq of KCl 74.5 mg

10 mEq of KCl x mg10 mEq of KCl x mg

x = 10 x 74.5 = 745 mgx = 10 x 74.5 = 745 mg


1



A dose of Calcium Chloride is given as 136 A dose of Calcium Chloride is given as 136 mg of calcium ions. How many milligrams of mg of calcium ions. How many milligrams of CaCl2 are needed? CaCl2 is available as the CaCl2 are needed? CaCl2 is available as the monohydrate (CaCl2.H2O), which has a MW monohydrate (CaCl2.H2O), which has a MW = 147; calcium ion has an atomic weight of = 147; calcium ion has an atomic weight of 40.40.


The power for oral solution for a bowel The power for oral solution for a bowel cleansing product contains 568 mg of cleansing product contains 568 mg of anhydrous Sodium Sulfate (Na2SO4). How anhydrous Sodium Sulfate (Na2SO4). How many milliequivalents of Na in this product? many milliequivalents of Na in this product? (MW of Na2SO4 = 142)(MW of Na2SO4 = 142)

Expressions of Quantity of DrugsExpressions of Quantity of Drugs Osmols and milliosmolsOsmols and milliosmols An osmol is the number of moles of solute present An osmol is the number of moles of solute present

multiplied by the number of particles per molecule when the multiplied by the number of particles per molecule when the solute is dissolved in water.solute is dissolved in water.

Nonelectrolytes such as dextrose do not dissociate therfore, one mole Nonelectrolytes such as dextrose do not dissociate therfore, one mole dextrose yields one osmol.dextrose yields one osmol.

Sodium chloride dissociates into two ions in aqueous solution Sodium chloride dissociates into two ions in aqueous solution therefore, one mole sodium chloride gives two osmols.therefore, one mole sodium chloride gives two osmols.

Sodium sulfate dissociate into three ions in aqueous solutions Sodium sulfate dissociate into three ions in aqueous solutions therefore, one mole sodium sulfate gives three osmolstherefore, one mole sodium sulfate gives three osmols

Milliosmols are often used in pharmacy and medicine.Milliosmols are often used in pharmacy and medicine.

Expressions of Quantity of DrugsExpressions of Quantity of Drugs Example Calculation 6Example Calculation 6 Isotonic Sodium Chloride Solution has 9 g of NaCl Isotonic Sodium Chloride Solution has 9 g of NaCl

in each liter of solution. How many osmols are there in each liter of solution. How many osmols are there in each liter of solution? (MW of NaCl = 58.5)in each liter of solution? (MW of NaCl = 58.5)

1 mole NaCl 58.5 g1 mole NaCl 58.5 g 1 mole NaCl 2 osmol1 mole NaCl 2 osmol 2 osmol 58.5 g2 osmol 58.5 g x osmol 9 gx osmol 9 g x = 2 x 9 = 0.308 osmolx = 2 x 9 = 0.308 osmol

58.5


Example Calculation 7Example Calculation 7 You want to add solute to a liter of water so You want to add solute to a liter of water so

that there are 300 mOsmol in this solution. that there are 300 mOsmol in this solution. Your source of solute is Magnesium Sulfate Your source of solute is Magnesium Sulfate Heptahydrate (MgSO4.7H2O), which has Heptahydrate (MgSO4.7H2O), which has MW = 246.5. How many milligrams of this MW = 246.5. How many milligrams of this solute should you add?solute should you add?

Expressions of ConcentrationExpressions of Concentration Concentration gives quantity of drugs or active ingredients Concentration gives quantity of drugs or active ingredients

per amount (volume or weight) of product or preparation. per amount (volume or weight) of product or preparation. Pharmaceutically useful expressions of concentration are:Pharmaceutically useful expressions of concentration are:1.1. Percentage weight in volume (w/v)Percentage weight in volume (w/v)2.2. Percentage volume in volume (v/v)Percentage volume in volume (v/v)3.3. Percentage weight in weight (w/w)Percentage weight in weight (w/w)4.4. Ratio strengthRatio strength5.5. Molarity (M)Molarity (M)6.6. Normality (N)Normality (N)7.7. Molality (m)Molality (m)8.8. Mole fraction (x)Mole fraction (x)

Expressions of ConcentrationExpressions of Concentration

Percentage weight in volume (w/v) indicates the number of Percentage weight in volume (w/v) indicates the number of grams of a constituent per 100 ml of solutiongrams of a constituent per 100 ml of solution

Percentage volume in volume (v/v) indicates the number of Percentage volume in volume (v/v) indicates the number of milliliters of a constituent in 100 ml of liquid formulation.milliliters of a constituent in 100 ml of liquid formulation.

Percentage weight in weight (w/w) indicates the number of Percentage weight in weight (w/w) indicates the number of grams of a constituent per 100 g of formulation (solid or grams of a constituent per 100 g of formulation (solid or liquid)liquid)

Ratio strength, as the name implies is the expression of Ratio strength, as the name implies is the expression of concentration by means of a ratio.concentration by means of a ratio.

Expressions of ConcentrationExpressions of Concentration Molarity (M) is the number of moles of solute per liter of Molarity (M) is the number of moles of solute per liter of

solution. solution. Molality (m) is the number of moles of solute per 1000 Molality (m) is the number of moles of solute per 1000

grams of solvent. grams of solvent. Normality (N) is the number of equivalents per liter of Normality (N) is the number of equivalents per liter of

solution.solution. Osmolality is the number of osmols per kilogram of Osmolality is the number of osmols per kilogram of

water. water. Osmolarity is the number of osmols per liter of solution.Osmolarity is the number of osmols per liter of solution. Mole fraction (x) is the ratio of the moles of one Mole fraction (x) is the ratio of the moles of one

constituent of a solution to the total moles of all constituent of a solution to the total moles of all constituents. To express in percentage, multiply x by 100. constituents. To express in percentage, multiply x by 100.



Diluted Hydrochloric Acid NF contains 10 g of Diluted Hydrochloric Acid NF contains 10 g of HCl in 100 ml of solution. Calculate its HCl in 100 ml of solution. Calculate its molarity. (MW of HCl = 36.5)molarity. (MW of HCl = 36.5)



You want to make 500 ml of a 1 M solution You want to make 500 ml of a 1 M solution of Sulfuric Acid. How many grams of H2SO4 of Sulfuric Acid. How many grams of H2SO4 do you need? (MW of H2SO4 = 98.1)do you need? (MW of H2SO4 = 98.1)

Expressions of ConcentrationExpressions of Concentration Example Calculation 10Example Calculation 10

Syrup NF contains 850 g of Sucrose in 1000 ml of solution. The Syrup NF contains 850 g of Sucrose in 1000 ml of solution. The solution has a density of 1.3. The MW of Sucrose = 342. solution has a density of 1.3. The MW of Sucrose = 342. Calculate the molarity and molality of the solution. Calculate the molarity and molality of the solution.

1 mole 342 g1 mole 342 g x mole 850 g x = 2.49 molex mole 850 g x = 2.49 mole there are 2.49 mole per liter, the concentration is 2.49Mthere are 2.49 mole per liter, the concentration is 2.49MFor molality: For molality: Weight of solution = 1000 ml x 1.3 g/ml = 1300 gWeight of solution = 1000 ml x 1.3 g/ml = 1300 gWeight of solvent = 1300 g – 850 g = 450 gWeight of solvent = 1300 g – 850 g = 450 g

2.49 mole 450 g2.49 mole 450 g x mole 1000 g x = 5.5 mole x mole 1000 g x = 5.5 mole there are 5.5 mole per 1000 g solvent, the concentration is 5.5 m.there are 5.5 mole per 1000 g solvent, the concentration is 5.5 m.

Expressions of ConcentrationExpressions of Concentration Example Calculation 11Example Calculation 11

A patient medical record from a former A patient medical record from a former hospitalization shows a cholesterol level of hospitalization shows a cholesterol level of 320 mg/dl. What is the equivalent of this 320 mg/dl. What is the equivalent of this level in mmol/l? (MW of cholesterol = 387)level in mmol/l? (MW of cholesterol = 387)



You want to make 500 ml of a 1 N solution of You want to make 500 ml of a 1 N solution of Sulfuric Acid. How many grams of H2SO4 Sulfuric Acid. How many grams of H2SO4 do you need? (MW of H2SO4 = 98.1)do you need? (MW of H2SO4 = 98.1)

1 Eq Wt. = 98.1 / 2 = 49 g1 Eq Wt. = 98.1 / 2 = 49 g

0.5 Eq Wt. = x0.5 Eq Wt. = x

x = 24.5 gx = 24.5 g



You have a pint of Potassium Chloride Syrup that is labeled You have a pint of Potassium Chloride Syrup that is labeled 10%. What is the concentration in mEq per one tablespoonful? 10%. What is the concentration in mEq per one tablespoonful? (MW of KCl = 74.5)(MW of KCl = 74.5)

10 g 100 ml10 g 100 ml x g 15 ml x = 1.5 gx g 15 ml x = 1.5 g 1 mEq 74.5 mg1 mEq 74.5 mg x mEq 1500 mg x = 20.1 mEqx mEq 1500 mg x = 20.1 mEq


Example Calculation 14Example Calculation 14 Sodium Chloride Injection is 0.9% NaCl. Sodium Chloride Injection is 0.9% NaCl.

Calculate its concentration in mOsmol/l. Calculate its concentration in mOsmol/l. (MW of NaCl = 58.5)(MW of NaCl = 58.5)

Test your selfTest your self

An aqueous solution of FeSo4 is prepared An aqueous solution of FeSo4 is prepared by adding 41.5 g FeSo4by adding 41.5 g FeSo4 to enough water to to enough water to make 1000 ml of solution. The density of make 1000 ml of solution. The density of the solution is 1.0375 and the MW of the solution is 1.0375 and the MW of FeSo4FeSo4 is 151.9. calculate: the molarity, the is 151.9. calculate: the molarity, the molality, the mole fraction of molality, the mole fraction of FeSo4 and FeSo4 and water, the mole percent of the two water, the mole percent of the two constituents, and the percent by weight of constituents, and the percent by weight of FeSo4.FeSo4.

Quantity and Concentration Expression. Expressions of Quantity of Drugs One molecule of a substance...

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