Physical Properties of Solutions

Physical Properties of Solutions14.4Electrical Conductivity in SolutionsConductivity: the ability to conduct electricityIn order to conduct, the substance must contain mobile charged particlesThese particles may be either ions or electrons In order for a solution to conduct electricity, it must contain ionsElectrical Conductivity of SolutionsElectrolyte: a substance that dissolves in water to give a solution that conducts an electric currentStrong electrolytes completely dissociate into ions and so conduct wellWeak electrolytes do not completely dissociate and therefore weakly conduct electricityNonelectrolyte: a liquid or solid substance that does not allow the flow of an electric current either is its pure state or in solution. E.g. water, sugar, CO2, sulfur dioxide

Electrical Conductivity of SolutionsAcids react with water to form the hydronium ion, H3O+. Weak Acids: In water, only about 1-10% of a weak acids molecules will ionize into solutionHNO2, CH3COOHStrong Acids: In water, 100% of a strong acids molecules will ionize into solution. HCl, HBr, HI, HNO3, H2SO4

Colligative PropertiesColligative Property: a property of a substance or system that is determined by the number of particles present in the system but independent of the properties of the particles themselvesColligative PropertiesAny solute contributes to the colligative properties of the solvent The identity of the solute is unimportant (must be nonvolatile)The degree of the effect depends on the concentration of the solute particles in a certain mass of solvent the more particles, the greater the effect!Colligative PropertiesC12H22O11 (s) C12H22O11 (aq)

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

CaCl2 (s) Ca2+ (aq) + 2Cl- (aq)

Vaporization is the process in which a liquid is converted to a gas.Colligative PropertiesColligative properties are all caused by a decrease in the vapor pressure of the solventSolute particles added to solution decreases the number of available solvent particles per volume fewer particles are available to vaporize decreased vapor pressureA decrease in vapor pressure = more heat to boil and a lower temperature to freezehttps://www.youtube.com/watch?v=re9r0kzQp_M Colligative PropertiesBoiling-point elevation:Boiling point: the temperature at which the liquids vapor pressure is equal to the atmospheric pressure above the liquidThe addition of solute particles decreases the number of solvent particles per volume available to vaporiseLess solvent particles lower vapor pressure more energy heat required to boilColligative PropertiesFreezing-point depression:The freezing point of water is the temperature at which the vapor pressure of water and ice are equalWith the addition of solute, the solvent particles are essentially diluted less solute, lower vapor pressureLower vapor pressure, lower temperature required to freeze to a solid

Colligative Properties - SummaryThe addition of a solute to a pure liquid solvent changes the properties of the liquidThe vapor pressure, boiling point and freezing point of a solution are colligative properties and depend upon the total number of solute particles rather than on their nature.The vapor pressure of a liquid is related to the tendency of the molecules to escape from a solution. For example, the proportion and escaping tendency of water molecules is decreased when a solute is dissolve in pure water, and the vapor pressure of the solution is therefore lower than that of pure waterDecreasing the vapor pressure of a solvent by the addition of a solute causes an increase in boiling point, a boiling-point elevationThe decrease in vapor pressure of a solvent resulting from the addition of a solute causes a corresponding decrease in its freezing point, a freezing-point depression. The concentration of the solute affects freezing- and boiling-point changes. The more particles, the greater the freezing-point depression and boiling-point elevation. SurfactantsSurfactant: a substance that concentrates at the boundary surface between two immiscible phases Solid-liquidLiquid-liquidGas-liquidhttps://www.youtube.com/watch?v=1baLzbathvI&spfreload=10 Detergent: a water-soluble cleaner that can emulsify dirt and oil. A surfactant for cleaning purposeshttps://www.youtube.com/watch?v=ZMhyD-wUPjo&spfreload=10

SurfactantsDetergent: a water-soluble cleaner that can emulsify dirt and oil. A surfactant for cleaning purposeshttps://www.youtube.com/watch?v=ZMhyD-wUPjo&spfreload=10 Soap: a substance that is used as a cleaner and dissolves in water. A natural detergent.Emulsion: any mixture of two or more immiscible liquids in which one liquid is dispersed in the other

Emulsifying Agents form a stable emulsion a colloidal suspension of one liquid in anotherHard WaterSoaps are actually salts when dissolved, they form ions. The non-polar hydrocarbon anion is what is soluble with dirt and oilsThese anions can form salts with dissolved cations that are found in high concentrations in hard water. 2C12H25COO-(aq) + Ca2+(aq) (C12H25COO)2Ca(s)Synthetic DetergentsSynthetic detergents were developed in the 1930s in an effort to overcome the precipitates problem caused by using soap with hardwaterThey have much the same structure as soap except that the long nonpolar tail of the detergent is connected to the salt of sulfonic acid SOOOH instead of the organic acid COOH.