This document discusses different methods of measuring solute concentrations in solutions. It defines key terms like solute, solvent, concentration, and explains common units of concentration like molarity and molality. Molarity is moles of solute per liter of solution, while molality is moles of solute per kilogram of solvent. The document also covers colligative properties, how solutions can be isotonic, hypertonic, or hypotonic, and different ways of expressing drug concentrations including parts ratio, percentage, and weight per volume.

1. MEASUREMENT OF
SOLUTE
CONCENTRATIONS

2. SOLUTION
• Homogenous, single-phase mixture of a solute & solvent.
Solvent
• The liquid component.
Solute
• The solid component, or liquid in lesser proportion.

3. Example of a solution
 Sea water
 Solvent: water, H2O
 Solute: NaCl

4. Example of a solution
 Air
 What is the solvent? Nitrogen, N2
 What is the solute? Oxygen, O2

5. Example of a solution
 18 ct gold
What is the solvent? Gold, Au
What is the solute? Copper, Cu

6. Terminologies
 Soluble substances are those that can
dissolve in a given solvent.
 Insoluble or immiscible substances are
those that cannot dissolve in a given
solvent.

7. Terminologies
 The maximum amount of a given solute a
solvent can dissolve is called the
solubility.
 The solubility is dependent on the
temperature and pressure.

8. Concentration of Solutions
 The CONCENTRATION of a solution is a
measure of the amount of solute that is
dissolved in a given solvent.
 DILUTE solution
 CONCENTRATED solution

10. EXP. OF
CONCENTRATION
Molarity
Per liter of solution
Molality
Per kg of solvent

11. Mole
 One mole is equal to 6.02 x 1023 particles, and the
mass of one mole of particles of a substance is
equal to that substance’s atomic or molecular
weight.
 Scientists often express concentration based on
moles of particles in a given volume of solution.

12. Mole
 To determine the no. of moles of a substance,
divide the mass by the molecular weight of that
substance.
Moles = mass (g)__________
molecular weight (g/mole)

13. Compute for mole
 Calculate the number of moles present in 117g of
NaCl.
Moles = 117 g___________
23.0 + 35.5 g/mole

14. Mole

15. 3 moles Ca2+ and 3 moles 2 Cl- which is 3 moles Ca2+ and 6 moles Cl-

16. Molality (m)
 The number of moles of solute in one kilogram of
solvent.
m = moles of solute
solvent mass (kg)

17. Molarity (M)
 Defined as the number of moles of a solute per
liter of solution.
M = moles of solute
solution volume (kg)

18. MOLALITY (m) MOLARITY (M)
M = moles of solute
solution volume(L)
m = moles of solute
solvent mass(kg)

19. MOLARITY
1 mole solute B
Add water to 1L solution
1 mole solute A
1 L1 L
Add water to 1L solution
Solute/Solvent ratio varies
Volume constant

20. 1 mole solute A
Pre-measure 1L (1kg) water
MOLALITY
1 1 mole solute B
Pre-measure 1L (1kg) water
Solute/Solvent ratio constant
Volume varies

21. 1 mole solute A
1 mole solute A
Add water to 1L solution Pre-measure 1L (1kg) water
MOLALITYMOLARITY

22. Molarity (M)
 Find for the mass of the solute, molecular weight
of that solute, and total volume of the solution.
M = moles of solute
solution volume (L)

23. Molarity: calculation (1)
 Determine the number of moles of solute
Moles of solute = _______mass(g)_______
molecular wt (g/mole)

24. Molarity: calculation (2)
 Divide the number of moles solute by the volume
of the solution .
M = moles of solute
solution volume (L)

25. Molarity: sample calculation
 If we were to mix 90g of glucose (MW =
180g/mole) in 2L of water*.
Moles solute = ______mass_(g)_______
molecular wt (g/mole)

26. Calculation
M = moles of solute
solution volume (L)
M = 0.5 moles = 0.25 M
2 L

27. Molarity Example
 If 5 liters of water is added to two moles of
glucose to make a solution, the
concentration (molarity) is said to be 0.4 M
2 mol of glucose
5 liters of soln. = 0.4 M

28. Molality & Osmolality
 MOLALITY – concerns molecular concentration.
 OSMOLALITY – refers to the particle concentration.
*One mole of any substance, regardless of weight,
contains the same number of molecules (Avogadro’s
No. 6.061 x 1023 particles/M.

29. Molality Example
 A solution of sodium chloride, containing 58.5 g
of NaCl dissolved in 1 kg water, has a molal
concentration of 1 mole/kg (1 mmol/kg).

30. Osmolality Example
 When 58.5 g of sodium chloride is dissolved in
water, such a solution will have an osmolality of
2 osmoles/kg (2000 mOsm/kg).
 This is because NaCl is fully ionized in water
into an equal amount of Na+ and Cl-.

31. Physical Properties (Solvent)
1. Boiling point
2. Freezing point
3. Osmotic pressure
4. Vapor pressure

32. Colligative Properties
 A property that depends only upon the
number of solute particles, and not upon
their identity, is called a colligative
property.

33. Colligative Properties
 Three important colligative properties of
solutions:
1. Vapor-pressure lowering
2. Boiling-point elevation
3. Freezing-point depression

34. Vapor-pressure lowering

35. Vapor-pressure lowering
 The decrease in a solution’s vapor pressure is
proportional to the number of particles the solute
makes in solution.
 If one osmole of solute is added to 1 kg water the
vapour pressure falls by 0.04 kPa (0.3 mmHg).

36. Freezing-point depression
 Defined as the difference in temperature between
the freezing point of a solution and the freezing
point of the pure solvent.
 It is proportional to the number of solute particles
dissolved in the solvent and does not depend
upon their identity.

37. Boiling-point elevation
 Defined as the difference in temperature between
the boiling point of a solution and the boiling point
of the pure solvent is the boiling-point elevation.
 The boiling point of water increases by 0.512°C
for every mole of particles that the solute forms
when dissolved in 1000 g of water.

38. Tonicity
 The effect that an extracellular solution has on
the osmotic movement of water into or out of
the cell is described by the tonicity of the ECF.
 Property of a solution in reference to a
particular membrane.

39. TONICITY
ISOTONIC HYPERTONIC HYPOTONIC

40. Isotonicity
 Isotonic solution: “equal tension”, equal
osmotic pressures.
 A cell in isotonic environment is in a state of
equilibrium with the ICF & ECF.
 The amount of solute is the same on the inside
and outside the cell.

41. ISOTONIC SOLUTION:
1. The solution concentration is equal on
both sides of the membrane .
2. There is no net concentration
difference across the cell membrane
3. Water moves back and forth, but
there is no net gain or loss of water.

42. Erythrocyte suspended in a isotonic solution.

43. Hypertonicity
 Results when a cell is placed into a solution
with a higher osmotic concentration that the
ICF*.
 Hypertonic: “greater tension”

44. HYPERTONIC SOLUTION:
1. The solution outside the cell is
more concentrated than inside.
2. There is more water inside the cell
and the water will move out of the
cell.
3. This causes the cell to shrink

45. Examples of erythrocytes suspended in isotonic and hypertonic
saline solutions.

46. Hypotonicity
 Results when a cell is placed in a solution with a
lower osmotic concentration (e.g., distilled
water).
 The osmotic pressure of the ECF is less than
that of the ICF.
 Water flows into the cell, causing it to swell.

47. HYPOTONIC SOLUTION:
1. The concentration inside the cell is
more concentrated than outside.
2. Therefore there is more water
outside of the cell, and water will
move into the cell.
3. This will cause the cell to swell.

48. Examples of erythrocytes suspended in isotonic, hypertonic and
hypotonic saline solutions.

49. CALCULATION: DRUG
SOLUTIONS

50. 3 Ways of expressing drug
concentrations of drugs in solution
1. Parts ratio
2. Percent concentration
3. Weight per volume (W/V), Volume per
volume (V/V), Weight per weight (W/W)

51. Concentration (Strength)
 Amount of dissolved solute in the solvent.
 If we are going to add more solute, we are
also going to increase the concentration.

52. PARTS RATIO
 No reference units of measurement;
relationship of solute to solution.
 Ex. 1:32 dilution

53. PARTS RATIO
 Parts per million (PPM)
 1 mg of solute in a kg or liter of solution
 1 mcg of solute in a gram or milliliter

54. % CONCENTRATION
 % = Parts of solute per 100 parts of a solution.
 % Weight to Volume (W/V)
 x no. of grams of solute in a 100 mL of
solution

56. WEIGHT PER VOLUME