THEME: THEME: Solution. Colligative properties Solution. Colligative properties

of biological liquids.of biological liquids.

associate prof. Bekus I.R. preparedassociate prof. Bekus I.R. prepared

PLAN1. The main concepts of solutions2. Types of solutions3. Heat effect of a dissolution4. Methods for expressing the

concentration of a solution5. Vapor pressure and Raoult’s law6. Colligative properties7. Factors Affecting Solubility

Solution Composition

Solution: A homogeneous mixture (mixed at level of atoms molecules or ions

Solvent:Solute:

The major componentThe minor component

The solute and solvent can be any combination of solid (s), liquid (l), and gaseous (g) phases.

Dissolution: Two (or more) substances mix at the level of individual atoms, molecules, or ions.

GENERAL PROPERTIES OF SOLUTIONSGENERAL PROPERTIES OF SOLUTIONS

1. A solution is a homogeneous mixture of two or more components.

2. It has variable composition.

3. The dissolved solute is molecular or ionic in size.

4. A solution may be either colored or colorless nut is generally transparent.

5. The solute remains uniformly distributed throughout the solution and will not settle out through time.

6. The solute can be separated from the solvent by physical methods.

TYPES OF SOLUTION

1. Depending upon the 1. Depending upon the total components total components present in the present in the solution:solution:

Binary solution (two components)

Ternary solution (three components)

Quaternary solution (four components)…..etc.

2. Depending upon the 2. Depending upon the abilityability of the dissolution of the dissolution

some quantity of the some quantity of the solute in the solvent:solute in the solvent:

• Saturated

• Unsaturated solution

• Supersaturated

3. Depending upon the physical states of the solute and solvent, the solution can be classified into the

following nine type:

Selected Acids and Bases

Acids Bases

Strong Strong Hydrochloric, HCl Sodium hydroxide, NaOH Hydrobromic, HBr Potassium hydroxide, KOH Hydroiodoic, HI Calcium hydroxide, Ca(OH)2

Nitric acid, HNO3 Strontium hydroxide, Sr(OH)2

Sulfuric acid, H2SO4 Barium hydroxide, Ba(OH)2

Perchloric acid, HClO4

Weak Weak Hydrofluoric, HF Ammonia, NH3

Phosphoric acid, H3PO4

Acetic acid, CH3COOH (or HC2H3O2)

Gas solution. Gaseous solutions have the structure that is typical of all gases. (Air, the gaseous solution with which we come in closest contact, is composed primarily of N2 (78 % by volume), O2 (21 %), and Ar (1 %), with smaller concentrations of CO2, H2O, Ne, He, and dozens of other substances at very low levels).

Liquid solutions have the internal structure that is typical of pure liquids: closely spaced particles arranged with little order. Unlike a pure liquid, how ever, a liquid solution is composed of different particles. Much of this chapter is devoted to the properties of liquid solutions, and special emphasis is given to aqueous solutions, in which the major component is water.

Two kinds of solid solutions are common. The first, the substitutional solid solution, exhibits a crystal lattice that has structural regularity but in which there is a random occupancy of the lattice points by different species.

Factors Affecting Solubility1. Molecular Interactions

Polar molecules, water soluble, hydrophilic (water loving)

(Vitamins B and C; water-soluble) Non-polar molecules, soluble in non-polar

molecules, hydrophobic (water fearing) (Vitamins A, D, K and E; fat-soluble)

Factors Affecting Solubility of Gases

1. Structure Effects

2. Pressure Effects

Henry's law

At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

An equivalent way of stating the law is that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

Henry's law

Where

p is the partial pressure of the solute in the gas above the solution

c is the concentration of the solute

kH is a constant with the dimensions of pressure divided by concentration.

According to Henry's Law, the solubility of a gas in a liquid

  1) depends on the polarity of the liquid

  2) depends on the liquid's density

  3) remains the same at all temperatures

 4) increases as the gas pressure above

the solution increases

 5) decreases as the gas pressure above the

solution increases

An aqueous solution consists of at least two components, the solvent (water) and the

solute (the stuff dissolved in the water).

Water is a chemical compound with the chemical formula H2O.

A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at standard ambient

temperature and pressure, but it often co-exists on Earth with its solid state, ice, and gaseous

state (water vapor or steam).Water also exists in a liquid crystal state near

hydrophilic surfaces.

Nonelectrolytes are substances such as sucrose or ethyl alcohol, which do not produce ions in aqueous solution.

Concentration units of a solutionThe concentration of a solution may be

defined as the amount of solute present in the solution.

1. Mass percentage (weight percentage):The mass percentage of a component in a

given solution is the mass of the component per 100 g of the solution.

mass percentage of the component =

2. Mole fraction: It is the number of moles of the solute dissolved per litre of the solution.

The amount of a given component (in moles) divided by the total amount (in moles).

X 100%mass of component

total mass of mixture

MV

m

V

n CM

Molarity (Concentration of Solutions)= M

M = = Moles of Solute MolesLiters of Solution L

solute = material dissolved into the solvent

In air , Nitrogen is the solvent and oxygen, carbon dioxide, etc. are the solutes.In sea water , Water is the solvent, and salt, magnesium chloride, etc. are the solutes.In brass , Copper is the solvent (90%), and Zinc is the solute(10%)

LIKE EXAMPLE

Calculate the Molarity of a solution prepared by bubbling 3.68g of Gaseous ammonia into 75.7 ml of solution. Solution:

Calculate the number of moles of ammonia:

3.68g NH3 X = 0.216 mol NH3

1 mol NH3

17.03g

Change the volume of the solution into liters:

75.7 ml X = 0.0757 L 1 L1000 mL

Finally, we divide the number of moles of solute by the volume of the solution:

Molarity = = ____________ M NH3

0.216 mol NH3

0.0757 L

Molarity

Molarity Example Problem 1

12.6 g of NaCl are dissolved in water making 344mL of solution. Calculate the molar

concentration.

moles soluteM =

L solution

112.6 g NaCl

58.44 =

1344 mL solution

1000

molNaClgNaCl

LmL

= 0.627 M NaCl

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?

therefore the

solution contains

1.25 mol NaCl

1 L solution1

250. mL = 0.250 L solution 1000

L

mL

1.25 mol NaCl0.250 L solution

1 L solution

NaCl

moles soluteM =

L solution

Volume x concentration = moles solute

= 0.313 mol NaCl

Molarity

Molarity Example Problem 3

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

therefore the

solution contains

0.75 mol NaCl

1 L solution1 mol NaCl

15 g NaCl = 0.257 mol 58.44 g NaCl

1 L solution0.257

0.75 mol NaClmol NaCl

NaCl

moles soluteM =

L solution

moles solute ÷ concentration = volume solution

= L solution0.34

3. MolalityIt is the number of moles of the solute dissolved per 1000 g (or 1 kg) of the solvent. It’s denoted by m or Cm Cm = (m) = Moles of solute/Weight of solvent in kg

orCm = (m) = Moles of solute * 1000/Weight of solvent in gramThe unit of Molality is m or mol/kg

mM

m

m

n C

solventsolute

solute

solvent

solutem

Molality

Calculate the molality of a solution consisting of 25 g of KCl Calculate the molality of a solution consisting of 25 g of KCl in 250.0 mL of pure water at 20in 250.0 mL of pure water at 20ooC?C?

First calculate the mass in kilograms of solvent using the density of solvent:

250.0 mL of H2O (1 g/ 1 mL) = 250.0 g of H2O (1 kg / 1000 g) = 0.2500 kg of H2O

Next calculate the moles of solute using the molar mass: 25 g KCl (1 mol / 54.5 g) = 0.46 moles of solute

Lastly calculate the molality: m = n / kg = 0.46 mol / 0.2500 kg = 1.8 1.8 mm (molal) solution (molal) solution

Molal (m)Example Problem 1

If the cooling system in your car has a capacity of 14 qts,

and you want the coolant to be protected from freezing down to -25°F, the label says to combine 6 quarts of antifreeze with 8 quarts of water. What is the molal concentration of the antifreeze in the mixture?

antifreeze is ethylene glycol C2H6O2

1 qt antifreeze = 1053 grams1 qt water = 946 grams

mol solutem=

Kg solvent

2 6 2

2 6 2

1053 g C H O6 Qts

1 Qt C H O

m =

2 6 2

2 6 2

1mol C H O

62.1 g C H O

2

2

946 g H O8 Qts

1 Qt H O

1 Kg

1000 g

= 13 m

4. Normality:It is the number of gram equivalents of the solute

dissolved per litre of the solution. It’s denoted by N or CN

(N)= CN = Number of gram equivalents of solute/Volume of solution in litres

or(N) = CN = Number of gram equivalents of solute *1000 /

Volume of solution in ml

Number of gram equivalents of solute = Mass of solute / Equivalent mass of solute

% (w/w) =

% (w/v) =

% (v/v) =

% Concentration

100xsolutionmasssolutemass

100xsolutionvolumesolutemass

100xsolutionvolumesolutevolume

Mass and volume units must match.

(g & mL) or (Kg & L)

% ConcentrationExample Problem 1

What is the concentration in %w/v of a solution containing 39.2 g of potassium nitrate in 177 mL of solution?

100mass solute

volume solution% (w/v) =

39.2100

177

g

mL = 22.1 % 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?

100volume solute

volume solution% (v/v) =

3.2100

6.5

L

L = 49 % v/v

% ConcentrationExample Problem 3

What volume of 1.85 %w/v solution is needed to provide 5.7 g of solute?

100 mL solution5.7 g solute

1.85 g solute

% (w/v) = 1.85 g solute

100 mL solution

= 310 mL Solution

g solute ÷ concentration = volume solution

We know:

g soluteg solute and

mL solution

We want to get:

mL solution

Colligative Properties

Colligative properties depend only on the number of solute particles present, not on the identity of the solute particles.

Among colligative properties are Vapor pressure lowering Boiling point elevation Freezing point depression Osmotic pressure

The vapor pressure necessary to achieve equilibrium with the pure solvent is higher than that required with the solution.

Consequently, as the pure solvent seeks to reach equilibrium by forming vapor, the solution seeks to reach equilibrium by removing molecules from the vapor phase. A net movement of solvent molecules from the pure solvent to the solution results. The process continues until no free solvent remains.

The extent of vapor pressure lowering depends on the amount of solute.

Raoult’s Law quantifies the amount of vapor pressure

lowering observed.

PA = XAPOA

where PA = partial pressure of the solvent vapor

above the solution (ie with the solute)

XA = mole fraction of the solvent

PoA = vapor pressure of the pure solvent

Highlights– 1886 Raoult's law , the partial

pressure of a solvent vapor in equilibrium with a solution is proportional to the ratio of the number of solvent molecules to non-volatile solute molecules.

– allows molecular weights to be determined, and provides the explanation for freezing point depression and boiling point elevation.

Ideal solutions are those that obey Raoult’s Law.

Real solutions show approximately ideal behavior when:

1)The solution concentration is low2)The solute and solvent have similarly sized molecules3)The solute and solvent have similar types of intermolecular forces.

Boiling Point Elevation and Freezing Point Depression

Solute-solvent interactions also cause solutions to have higher boiling points and lower freezing points than the pure solvent.

For example, the addition of salt to water causes the water to freeze below its normal freezing point (0°C) and to boil above its normal boiling point (100°C).

At the normal boiling point of the pure liquid, the vapor pressure of the liquid, Po = 1 atm.

Freezing point depressionThe freezing point of a solution is the temperature at which the

first crystals of pure solvent begin to form.

Osmotic Pressure To stop osmosis, the chemical potential of the solvent in the

more concentrated solution can be increased by forcing the molecules closer together under an externally applied pressure.

The pressure required to stop osmosis, known as osmotic pressure, , is

= (n/v)RT = MRT where n is number of moles of solute, V volume of solution, M is the molarity of the solution T is thermodynamic temperature R is gas constant

Classification of Solutions According to Their Osmotic Pressure:

Hypertonic Hypotonic Isotonic Isotonic: The solutions being compared have equal

concentration of solutes. Hypertonic: The solution with the higher concentration of

solutes. Hypotonic: The solution with the lower concentration of

solutes.

Osmosis in Blood Cells

If the solute concentration outside the cell is greater than that inside the cell, the solution is hypertonic.

Water will flow out of the cell, and crenation (shrinking) results.

The effect of hypertonic and hypotonic solutions on animal cells.The effect of hypertonic and hypotonic solutions on animal cells.а) Hypertonic solutions cause cells to shrink (crenation) - plasmolysis;а) Hypertonic solutions cause cells to shrink (crenation) - plasmolysis;b) Hypotonic solutions cause cell rupture - hemolysis; b) Hypotonic solutions cause cell rupture - hemolysis; c) Isotonic solutions cause no changes in cell volume.c) Isotonic solutions cause no changes in cell volume.

Plasmolysis is the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis. This occurs in a hypertonic solution. The reverse process, cytolysis, can occur if the cell is in a hypotonic solution resulting in a lower external osmotic pressure and a net flow of water into the cell.

Difference between osmosis and diffusionDifference between osmosis and diffusion

van 't Hoff factor

The van 't Hoff factor is a measure of the effect of a solute upon colligative properties such as osmotic pressure, relative lowering in vapor pressure, elevation of boiling point and freezing point depression. The van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved, and the concentration of a substance as calculated from its mass.

For most non-electrolytes dissolved in water, the van' t Hoff factor is essentially 1. For most ionic compounds dissolved in water, the van 't Hoff factor is equal to the number of discrete ions in a formula unit of the substance.

Van't Hoff

The Person Behind the Science

J.H. van’t Hoff (1852-1901)

Highlights– Discovery of the laws of chemical

dynamics and osmotic pressure in solutions

– Mathematical laws that closely resemble the laws describing the behavior of gases.

– his work led to Arrhenius's theory of electrolytic dissociation or ionization

– Studies in molecular structure laid the foundation of stereochemistry.

Moments in a Life– 1901 awarded first Noble Prize in

Chemistry

van’t Hoff Factor (i)

dissolved solute of moles

solutionin particles of moles i

ΔT = − i m K

Oncotic pressureOncotic pressure, or colloid osmotic pressure, is a form of

osmotic pressure exerted by proteins in a blood vessel's plasma (blood/liquid) that usually tends to pull water into the circulatory system. It is the opposing force to hydrostatic pressure.

Throughout the body, dissolved compounds have an osmotic pressure. Because large plasma proteins cannot easily cross through the capillary walls, their effect on the osmotic pressure of the capillary interiors will, to some extent, balance out the tendency for fluid to leak out of the capillaries.

Raoult's law The vapour pressure of an ideal solution is

directly dependent on the vapour pressure of each chemical component and the mole fraction of the component present in the solution.

Where: pi: pressure of component i xi: mole fraction in the solution

: vapor pressure of the pure substance

CRYOSCOPY and EBULIOSKOPY

Determination of molecular weight substance freezing temperature decrease or increase the boiling point of solutions called according cryoscopy (cryoscopic method) or ebulioskopy (ebulioskopic method).

These methods are used to establish the composition of compounds to determine the degree of dissociation of

electrolytes, the study of the polymerization agents and associations in solutions.

Ware chemical

dishes chemical

A Petri dish (or Petri plate or cell culture dish) is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells or small moss plants.

Beaker A beaker is a simple

container for stirring, mixing and heating liquids commonly used in many laboratories. Beakers are generally cylindrical in shape, with a flat bottom. Most also have a small spout (or "beak") to aid pouring as shown in the picture. Beakers are available in a wide range of sizes, from one millilitre up to several litres.

Laboratory flasks

There are several types of laboratory flasks, all of which have different functions within the laboratory. Flasks, because of their use, can be divided into:

1. Reaction flasks

2. Multiple neck flasks

3. Schlenk flask

4. Distillation flasks

5. Reagent flasks

6. Volumetric flask

Volumetric flask A volumetric flask

(measuring flask or graduated flask) is a piece of laboratory glassware, a type of laboratory flask, calibrated to contain a precise volume at a particular temperature. Volumetric flasks are used for precise dilutions and preparation of standard solutions.

Graduated cylinder

A graduated cylinder, measuring cylinder or mixing cylinder is a piece of laboratory equipment used to measure the volume of a liquid. Graduated cylinders are generally more accurate and precise than laboratory flasks and beakers

Burette A burette is a device used in

analytical chemistry for the dispensing of variable, measured amounts of a chemical solution. A volumetric burette delivers measured volumes of liquid. Piston burettes are similar to syringes, but with precision bore and plunger. Piston burettes may be manually operated or may be motorized.

Funnels (laboratory)

Laboratory funnels are funnels that have been made for use in the chemical laboratory. There are many different kinds of funnels that have been adapted for these specialized applications. Filter funnels, thistle funnels (shaped like thistle flowers), and dropping funnels have stopcocks which allow the fluids to be added to a flask slowly. For solids, a powder funnel

Glass tubes

Glass tubes are hollow pieces of borosilicate or flint glass used primarily as laboratory glassware. Glass tubing is commercially available in various thicknesses and lengths. Glass tubing is frequently attached to rubber stoppers.

chemical dropper

A pipette, pipet, pipettor or chemical dropper is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser.

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