مترولوجي

 Concentration& Metrologypractical pharmacololgy 

By Dr.ABEER MANSOUR

CONTENT

Concentration
Solvent Solute

DEFINITIONS

DEFINITIONS

mass

DEFINITIONS



Volume concentration:The volume concentration (do not confuse with volume fraction[ is defined as the volume of a constituent divided by the volume of the mixture

Molarity Parts ratio Mole Fraction Molality

Concentration of Solution
Moles of solute
Liter of solution
(M)
=
=
Mol
L
amount of solute (g or ml)
amount of solution (g or ml)
(102) or (106) or (109)
Moles of solute
Total moles of solution
(c)
=
=
Mass of solvent
Moles of solute
(m)
=

Molarity

Molarity Example Problem 1
12.6 g of NaCl are dissolved in water making 344mL of solution. Calculate the molar concentration.
NaCl

Molarity

Molarity Example Problem 2
How many moles of NaCl are contained in 250.mL of solution with a concentration of 1.25 M?
NaCl
Volume x concentration = moles solute

Molarity

Molarity Example Problem 3
What volume of solution will contain 15 g of NaCl if the solution concentration is 0.75 M?
NaCl

% (w/w) =

% (w/v) =


% (v/v) =

% Concentration

Mass and volume units must match. (g & mL) or (Kg & L)

% Concentration

Example Problem 1
What is the concentration in %w/v of a solution containing 39.2 g of potassium nitrate in 177 mL of solution?
% (w/v) =
Example Problem 2
What is the concentration in %v/v of a solution containing 3.2 L of ethanol in 6.5 L of solution?
% (v/v) =

% Concentration

Example Problem 3
What volume of 1.85 %w/v solution is needed to provide 5.7 g of solute?
% (w/v) =

We know:

We want to get:


ppm =

ppb =

Parts per million/billion (ppm & ppb)
Mass and volume units must match. (g & mL) or (Kg & L)
or
or
= ppm
= ppb
AND For very low concentrations:
= ppt
parts per trillion

ppm & ppb

Example Problem 1
An Olympic sized swimming pool contains 2,500,000 L of water. If 1 tsp of salt (NaCl) is dissolved in the pool, what is the concentration in ppm?
1 teaspoon = 6.75 g NaCl
or

ppm & ppb

Example Problem 2
An Olympic sized swimming pool contains 2,500,000 L of water. If 1 tsp of salt (NaCl) is dissolved in the pool, what is the concentration in ppb?
1 teaspoon = 6.75 g NaCl
or

Mole Fraction

Mole Fraction (c)
A
B
B
B
B
B
A
A
A
A
A
A
A
A
c A =
moles of A
sum of moles of all components
A
B
A
+
c B =
moles of B
sum of moles of all components
B
B
A
+
Since A + B make up the entire mixture, their mole fractions will add up to one.

Mole Fraction

Example Problem 1
In our glass of iced tea, we have added 3 tbsp of sugar (C12H22O11). The volume of the tea (water) is 325 mL. What is the mole fraction of the sugar in the tea solution?(1 tbsp sugar ≈ 25 g) First, we find the moles of both the solute and the solvent.
Next, we substitute the moles of both into the mole fraction equation.

Mole Fraction

Example Problem 2
Air is about 78% N2, 21% O2, and 0.90% Ar. What is the mole fraction of each gas?
First, we find the moles of each gas. We assume 100. grams total and change each % into grams.
Next, we substitute the moles of each into the mole fraction equation.

Metrology

Metric System

The Apothecary System