CHE 112 - MODULE 1 CHAPTER 12 LECTURE NOTES. Properties of Gases Gases completely fill their...
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Transcript of CHE 112 - MODULE 1 CHAPTER 12 LECTURE NOTES. Properties of Gases Gases completely fill their...
CHE 112 - MODULE 1
CHAPTER 12
LECTURE NOTES
Properties of Gases
Gases completely fill their container in a uniform manner
Gases are compressible Gases have low densities Gases will exert pressure as the gas
molecules collide with the inner surfaces of their container
Kinetic Molecular Theory of Gases
A gas is composed of particles that are very small compared with the average distance between the individual particles.
Gas particles are in constant straight line, random motion.
Collisions are elastic. Attractions between particles are negligible. The average kinetic energy (energy of
motion) of these particles is directly proportional to the temperature in Kelvin.
Boyle’s Law
P 1/ V; PV = k when T is constant P = pressure & V = volume The pressure is inversely proportional to
the volume. As the pressure increases, the volume
decreases; and as the pressure decreases, the volume increases.
P1V1 = P2V2
Charles Law
V T; V = kT when P is constant V = volume & T = temp in Kelvin The volume is directly proportional to
the temperature. As the temp increases, the volume
increases: and as the temp decreases, the volume decreases.
V1/T1 = V2/T2
Combined Gas Law
Combination of Boyle’s and Charle’s Laws
P1V1 / T1 = P2V2 / T2
Used when all the conditions of the same gas changes, and nothing remains constant.
Avogadro’s Law
The molar volume is defined as the volume of 1 mole = 22.4 L for any gas at Standard Temperature and Pressure (STP)
STP means 273.15K (0°C) and 1 atm (760mm Hg)
Ideal Gas Law
PV = nRT P = pressure (atm) V = volume (L) n = number of moles (mol) R = gas constant = 0.08206 (L·atm/mol·K) T = temperature (K)
Real Gas Law
As temperatures and pressures deviate from STP, the Ideal Gas Law no longer holds true.
The Van der Waals equation is used to compensate for intermolecular forces and molecular volume in non-ideal conditions.
(P+a[n/V]2)(V-bn) = nRT
CHE 112 - MODULE 1
CHAPTER 13
LECTURE NOTES
Intermolecular Forces Dipole-dipole interactions
– polar molecules attract by charge Dipole-induced dipole forces
– a dipole can be induced by a polar species London dispersion forces
– momentary attraction of non-polar molecules Hydrogen bonding
– attraction of H-O, H-N and H-F with other highly electronegative atoms
Water and Hydrogen Bonding
The O of a water molecule attaches to four other water molecules
The hydrogen bonded water creates a tetrahedral of H around the O
Water freezes into a water lattice that is ordered and has spaces within the repeated lattice crystal
DNA and Hydrogen Bonding
Deoxyribonucleic acid (DNA) is a chain of phosphates linked to sugars
Bonded to each sugar is either a thymine, guanine, cytosine, or adenine base molecule
The base molecules on one chain interact through hydrogen bonding with base molecules on another chain
This pairing of chains produces the double helix of DNA
Properties of Liquids
Vaporization = H°vap standard molar heat of vaporization– liquid gas, endothermic process– liquid vapor, vapor pressure– boiling point
Surface tension - energy to break the surface Capillary action - adhesive forces Viscosity - resistance to flow
Vapor Pressure
Vapor pressure = the partial pressure of the vapor over the liquid, measured at equilibrium– As surface molecules gain sufficient KE, they
escape the liquid into vapor above the liquid– As the # of vapor molecules increase, more
collisions will occur above the liquid– More molecules will collide at the surface and
condense back into the liquid state– Rate of condensation = rate of vaporization– At this point, the partial pressure exerted = vapor
pressure of the liquid– As the temperature , KE , vapor pressure
Boiling Point Boiling point = the temperature at which the
vapor pressure of a liquid = the vapor pressure exerted on the liquid*– As temperature , vapor pressure ; when the
vapor pressure = atmospheric pressure, stable bubbles of vapor form
– The liquid begins to “boil”– Once boiling begins, it will continue to boil as long
as heat is supplied or until all the liquid has been converted to vapor
*At 1atm, water will boil at 100°C, but at the top of Whiteface, water will boil at a lower temperature
Types of Solids
Ionic compounds Metallic materials Molecular compounds Network solids Amorphous materials
Crystalline vs Amorphous
Crystalline = has a defined structure Amorphous = random (undefined
structure)
Cubic Units
Simple cube Face-centered cube Body centered cube
Phase Diagrams
Phase Diagram shows all the phases of matter and their relationships for different types of matter– Solid– Liquid– Gas– Triple point– Critical point
Changes of States
Melting (solid > liquid) Freezing (liquid > solid) Vaporization (liquid > vapor) Condensation (vapor > liquid) Sublimation (solid > vapor) Condensation by deposition (vapor >
solid)
CHE 112 - MODULE 1
CHAPTER 14
LECTURE NOTES
Units of Concentration
Molarity (M) = moles of solute Liters of solution
Molality (m) = moles of solute Kg of solvent
Mole fraction (XA) = moles of A moles of solution
Units of Concentration (cont.)
Weight % A = mass of A X 100%
total mass
Parts per million (ppm) = 1g of matter
mass million g
1ppm = 1mg/L = 1g/ml
Solutions
Saturated - solution containing the maximum amount of dissolved solvent
Unsaturated - Less than saturated
Supersaturated - more than saturated
Liquid/Liquid Interaction
Miscible - liquids that mix well due to like polarity
Immiscible - liquids that do not mix because one is polar and the other is non-polar
“Likes dissolve likes”
Solids Dissolved in Liquids
Hydrated - ionic solids dissolve when surrounded by polar water molecules in solution
Heat of Solution (Hsoln) = net energy change for the solution process– Exothermic rxn yield more soluble cmp– Endothermic rxn yield insoluble cmp
Enthalpy of Hydration
The energy involved with hydrating an ion depends on 3 things:– distance between the ion & dipole (closer
the stronger attraction)– charge on the ion (higher the stronger)– polarity of the solvating molecule (greater
the magnitude of the dipole the stronger)
Vapor Pressure Lowering
VPL = a colligative property (concentration dependent) equal to the vapor pressure of pure solvent minus the vapor pressure of the solution– Occurs when a nonvolatile solute is mixed
with a solvent that have similar structure Psolv = Psolv - Psolv
Raoult’s Law
Psolv = XsolvP solv
– Psolv Xsolv
– Vapor pressure of the solution is lower than the that of the pure solvent
– CD-ROM Screen 14.7
Psolv = -XsolvPsolv
Freezing Point Depression
Freezing point depression is a colligitive property equal to the freezing point of the pure solvent minus the freezing point of the solution
Tfp = kfp msolute
Tfp = freezing point depression– kfp = freezing point depression constant (for water it
is -1.86°C/m)– msolute = molal concentration
Boiling Point Elevation
Boiling point elevation is a colligitive property equal to the boiling point of the solution minus the boiling point of the pure solvent
Tbp = kbp msolute
Tbp = boiling point elevation
– kbp = boiling point elevation constant (for water it is 0.512°C/m)
– msolute = molal concentration
Colloids
Dispersion of particles of one substance (dispersed phase) throughout another substance or solution (the continuous phase)
Appears homogeneous Particle sizes are between 10 – 2000
angstroms (1x10-10m) in diameter
Micelle
Aggregate of molecules that have a polar end and a nonpolar end.– Nonpolar ends will meet together in the
middle, while the polar ends will be attracted outward toward the water molecules