Chemistry 21A Dr. Dragan Marinkovic SOLUTIONS. A solution is a homogeneous mixture of a solute and a solvent. Solutions can be formed in any state of

Chemistry 21A Dr. Dragan Marinkovic

SOLUTIONS

SOLUTIONS

A solution is a homogeneous mixture of a solute and a

solvent. Solutions can be formed in any state of matter; that is they may be solid, liquid, or gas.

A solution is prepared by dissolving a solute into

the solvent.

Solute is either the smaller component of a mixture or, when liquid solutions are considered, the gaseous or solid substance added to the solution.

Solutions could be composed of either complete molecules (atoms) - molecular solution, or ions - ionic solution. The latter usually is referred to aqueous solutions of salts. Fluids that mix or dissolve in

each other in all proportions are call miscible fluids, lacking

that property fluids are called immiscible. So gases are always miscible

miscible immisciblesoluble insolublesaturated unsaturated solutiondissolve precipitate (crystallize)

supersaturatedsolution


SOLUTIONS

SOLUBILITY The maximum amount of solute that can be dissolved in a specific amount of solvent at specific temperature and pressure.

NaCl(s) <==> Na+(aq) + Cl-(aq)If there is more solute dissolved than

saturation allows, the solution is said to be supersaturated. supersaturated

solution


SOLUTIONS

Solubility in water with temperature under 1 atm pressure, units of solubility in g/100g H2O. Substance Formula 0°C 10°C 20°C 30°C 40°C

Helium He 0.6

Hydrogen chloride HCl 81 75 70 65.5 61

Fructose C6H12O6 375.0 538.0Ammonia NH3 1176 900 702 565 428(Unit:mL/mL)Ammonium chloride NH4Cl 29.4 33.2 37.2 41.4 45.8Calcite CaCO3 0.0006Magnesium carbonate MgCO3 0.039Magnesium chloride MgCl2 52.9 53.6 54.6Oxygen O2 .0015 0.0011 0.0009 0.0008 0.0006


SOLUTIONS

solute solubility (g solute in 100 g water)

solubility term

less than 0.1 insoluble

0.1 - 1slightly soluble

1 - 10 soluble

greater than 10 very soluble Chemistry 21A Dr. Dragan Marinkovic

SOLUTIONS


SOLUTIONS

‘LIKE DISSOLVES LIKE”Polar solvents will dissolve polar or ionic solutes and nonpolar solvents will dissolve nonpolar or nonionic solutes.


SOLUTIONS


SOLUTIONS

Heat of SolutionThe process of dissolving is a process which involves the breaking and making of bonds, and that involves energy.

The formation of bonds releases energy. That is called exothermic. If more energy is released in making bonds than is used in breaking bonds, the process is exothermic.

Dissolution overall can be either endothermic or exothermic, depending on whether more energy was used to break the bonds, or more energy was released when new bonds were formed. The breaking of bonds requires or absorbs energy. Using energy like that is called endothermic. If more energy is used than is released, the process is endothermic.SOLUTE + SOLVENT + HEAT SOLUTION

SOLUTE + SOLVENT SOLUTION + HEAT


SOLUTIONS

CONCENTRATION

RED DYE

Concentration -- amount of a solute present in a solution per standard amount of solvent

Molarity (M): This unit of concentration Relates the moles of solute per liter of solution.

Weight/Weight Percent (w/w%): This unit of concentration is often used for concentrated solutions, typically acids and bases. If you were to look on a bottle of a concentrated acid or base solution the concentration expressed as a weigh/weight percent.

milliliters of solution

w/v%

v/v%solute volume

solution volume


SOLUTIONS

SOLUTION PREPARATION

milliliters of solution

w/v%

v/v%solute volume

solution volume

Solutions are prepared by mixing proper amounts of solute and solvent or by diluting a concentrated solution by a solvent to produce a solution of lower concentration.

a single ring graduation mark

mass m

density = --------- = ----

= d volume V

m = d x V


SOLUTIONS

SOLUTION PREPARATION

Dilution is preparing a solution of lower concentration by diluting a solution of higher concentration (“stock solution”).

There is an element of simplicity in calculations. The number of moles of solute in the concentrated solution is equal to the number of moles in the dilute solution. You have simply increased the amount of solvent in the solution.

molescon = molesdil

This equation is true for any solution concentration based on volume.

(Mconc) (Vconc) = (Mdil) (Vdil)


SOLUTIONS

SOLUTION PROPERTIES

Electrolyte is chemical compound that ionizes when dissolved in water to produce an electrically conductive medium.

Nonelectrolyte is chemical compound that does not ionize when dissolved in water and does not produce an electrically conductive medium.

WATERSUGAR SOLUTION

NaCl SOLUTION

NaCl(aq) Na+(aq) + Cl -(aq)


SOLUTIONS

SOLUTION PROPERTIES

The vapor pressure of a solution is lower than that of the pure solvent

Boiling point elevation

Freezing point depression

Vapor pressure depression


SOLUTIONS

SOLUTION PROPERTIES

Colligative property of a solution depends only on the ratio of the number of particles of solute and solvent in the solution, not the identity of the solute.

∆t = nKm

molalitykg solvent

= m = M

∆t = boiling orfreezing point difference

Kf = freezing constant

characteristic for the solvent used

The factor n accounts for the number of individual particles (typically ions) formed by a compound in solution. Examples: n = 1 for sugar in watern = 2 for sodium chloride in water, due to the full dissociation of NaCl into Na+ and Cl-

n = 3 for calcium chloride in water, due to dissociation of CaCl2 into Ca2+ and 2Cl-

K = constant characteristic for the solvent used

Kb = boiling constant characteristic for the solvent used

≈For diluteSolutions.


SOLUTIONS

SOLUTION PROPERTIES

Solvent Boiling Point (°C) Kb(°C/(mol

kg-1)) Freezing

Point (°C) Kf (°C/(mol

kg-1)) Data source

Acetic Acid 118.1 3.07 16.6 –3.90 Kb Kf

Acetone 56.2 2.67 –94.8 Kb

Benzene 80.1 2.65 5.5 –4.90 Kb & Kf

Camphor 204.0 5.95 179 –40 Kf

Carbon disulfide 46.2 2.34 –111.5 –3.83

Chloroform 61.2 3.88 –63.5 –4.90 Kb & Kf

Cyclohexane 80.74 2.79 6.55 –20.2

Diethyl ether 34.5 2.16 –116.2 –1.79 Kb & Kf

Ethanol 78.4 1.19 –114.6 –1.99 Kb

Water 100.00 0.52 0.0 –1.86 Kb & Kf

∆t = nKm


SOLUTIONS

SOLUTION PROPERTIES

Osmosis transfer of a liquid solvent through a semipermeable membrane that does not allow dissolved solids (solutes)

to pass. Osmosis refers only to transfer of solvent; transfer of solute is called dialysis. In either case the direction of transfer is from the area of higher concentration of the material transferred to the area of lower concentration. This spontaneous migration of a material from

a region of higher concentration to a region of lower concentration is called diffusion.

Osmosis

In osmosis,water (solvent) flows from the lower solute concentration into the higher solute concentration. The level of the solution with the higher concentration rises. The concentrations of the two solutions become equal with time.


SOLUTIONS

SOLUTION PROPERTIES

Setup for Measuring the Osmotic Pressure of a Solution

Osmotic pressure is the hydrostatic pressure produced by a difference in concentration between solutions on the two sides of a surface such as a semipermeable membrane.

π = nMRT temperature (K)

molality universal gas constant

The factor n accounts for the number of individual particles


SOLUTIONS

SOLUTION PROPERTIES

Red blood cells have cell walls that are semipermeable membranes.Maintain an osmotic pressure that cannot change or damage occurs. Must maintain an equal flow of water between the red blood cell and its surrounding environment.

An isotonic solutionexerts the same osmotic pressure as red blood cells.

is known as a “physiological solution”.

of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells.


SOLUTIONS

SOLUTION PROPERTIES

In dialysis,solvent and small solute particles pass through an artificial membrane.Large particles are retained inside.Waste particles such as urea from blood are removed using hemodialysis (artificial kidney).

This graphic illustrates the dialysis process. First, the concentrated protein solution is placed in dialysis bag with small holes which allow water and salt to pass out of the bag while protein is retained. Next the dialysis bag is placed in a large volume of buffer and stirred for many hours (16 to 24 hours), which allows the solution inside the bag to equilibrate with the solution outside the bag with respect to salt concentration. When this process of equilibration is repeated several times (replacing the external solution with low salt solution each time), the protein solution in the bag will reach a low salt concentration:


SOLUTIONS

SOLUTION PROPERTIES

In hemodialysis, the patient's blood is pumped through the blood compartment of a dialyzer, exposing it to a semipermeable membrane. The cleansed blood is then returned via the circuit back to the body. Ultrafiltration occurs by increasing the hydrostatic pressure across the dialyzer membrane.


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Chemistry 21A Dr. Dragan Marinkovic SOLUTIONS. A solution is a homogeneous mixture of a solute and a solvent. Solutions can be formed in any state of