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SOLUTIONS. Chemistry 21A Dr. Dragan Marinkovic. SOLUTIONS. - PowerPoint PPT Presentation
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Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONS
SOLUTIONSA 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)supersaturated
solution
Chemistry 21A Dr. Dragan Marinkovic
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
Chemistry 21A Dr. Dragan Marinkovic
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
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONS
solute solubility (g solute in 100 g water)
solubility term
less than 0.1 insoluble
0.1 - 1 slightly soluble
1 - 10 soluble
greater than 10 very soluble Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONS
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONS
‘LIKE DISSOLVES LIKE”Polar solvents will dissolve polar or ionic solutes and nonpolar solvents will dissolve nonpolar or nonionic solutes.
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONS
Chemistry 21A Dr. Dragan Marinkovic
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
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSCONCENTRATION
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 solutionw/v%
v/v%solute volume
solution volume
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION PREPARATION
milliliters of solutionw/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 mdensity = --------- = ---- = d volume Vm = d x V
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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)
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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.
WATER SUGAR SOLUTION
NaCl SOLUTION
NaCl(aq) Na+(aq) + Cl -(aq)
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION PROPERTIES
The vapor pressure of a solution is lower than that of the pure solvent
Boiling point elevation
Freezing point depression
Vapor pressure depression
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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.
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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.
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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.
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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:
Chemistry 21A Dr. Dragan Marinkovic
SOLUTIONSSOLUTION 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.
Chemistry 21A Dr. Dragan Marinkovic