Intermolecular forces: Solids, Liquids, and Solutions Flashcards
Polarizability
What is Polarizability?
- Ability to induce another nonpolar molecule to have a momentary dipole between instantaneuous and indused dipole
- Happens with Covalent Compounds
IMF Trends
LDF Trends
- Increased = Increased size
- Increased = Increased polarizability
- Increased = Greater Charge Separation
Dipole-Dipole forces
What are they?
- Polar molecules with positive “end” and negative “end” which have a permanent dipole which attracts other dipoles when closer
- Stronger than LDF
Important Note!
What to do with LDF on Test
- Write full form: London Dispersion Forces
Hydrogen bonds
Conditions
- H has to be attached to F,O,N
- Other end is also F,O,N with/without H
Hydrogen bonds
What are they?
- Strong and special d-d
- Have to write both d-d + h-b
- bet H proton and negative side of F,O,N
Surface Tension
Definition
- Amount of energy required to stretch
- Increased surface of liquid by 1 unit area
- Higher IMFs = Higher ST
Surface Tension
Adhesion
IMFs between unlike molecules
Surface Tension
Cohesion
IMFs between like molecules
Viscocity
Definition
- Measure of a fluid’s resistance to flow
- Increased T = Decreased V
- Increased V = Increased IMFs
- Tangling ==> Increased V
H2O
Properties
- Excellent Solvent
- High Specific heat
- Ice Density is less than Water because struct for spread out
Liquid-Vapor Equilibrium
Vapor Pressure
- Partial pressure of liquids once equilbrium is established between gases and liquids
- Book Definition: Gaseous molecules pressure form evap. liquid
Liquid-Vapor Equilibrium
Dynamic Equilbrium
- Rate of forward process(l–>g) = Rate of backward process(g–>l)
- Constant Pressure
Liquid-Vapor Equilibrium
When is Boiling Point?
- When Vapor Pressure is equal to External pressure
Phase Changes
Critical Point
- Temperature that gas cant become a liquid no matter the pressure
IMF Trends
How are physical characteristics affected by IMFs?(only writing abt. high)
BP, VP, Viscocity, ST, Cohesive Forces
- Higher BP
- Lower VP
- Higher viscocity
- Higher ST
- High Cohesive Forces
Hydrogen Bonding
Salicylic Acid
- H-Bonding within molecule
Chromatography Lab
Rf
solute Distance/ Solvent Distance
VP Curves
Equation
- ln(Pvap1, T1/Pvap2, T2)=(∆Hvap/R)((1/T2)-(1/T1))
Alloys
Definition
- Solid Soln consisting of 2+ metals or metals with 1 + nm
Covalent Network Solids
Definition
- Network of covalently-bonded atoms into 2D and 3D network, holding it firmly together
Covalent Network Solids
Allotropes
- Elements exist in 2 diff formes in same physical state
- Ex) diamond and graphite for carbon
Semiconductors
Definitions
- Elements that are normally not conductors but are at high Temperatures or when coombined with other elements
Semicoductors
N-type
- Have an extra electron from bonding which can be used to create a voltage
- Donor Impurities
Semiconductors
P-type
- Have 1 less electron which creates “positive holes” that constatnly shift and allow current to flow through holes
- Acceptor Impurities
Physical Properties of Solns
Solvents
- determine soln’s state of matter
- usually majority component
Physical Properties of Solns
Solutes
- Substance dissolbed/dispersed in the solvent
Physical Properties of Solns
Solution Concentration
- Amnt of solute/ amount of solvent/soln
Physical Properties of Solns
Molality(m)
- moles of solute/ kg of solvent
- varies with mass of solvent and is independent of temperature
Physical Properties of Solns
Enthalpy of Soln
- Combination of Heat required breaking IMFs of solute and solvent plus the heat released for letting them mix
Physical Property of Solutions
Non-Ideal Solutions
- Not additive solutions(adding two solutions doesn’t result in a solutions with both that is not equal than combined amount: Ex) 50mL +50mL≠100mL)
- Happens due to unequal IMFS
- example of Ideal Mixture = Benzene and Methylbenzene
Physical Properties of Solutions
How Heat of Solution impacts ideality
- If = 0, Ideal
- If < 0, stronger solute-solvent forces; exothermic
- If > 0, weaker solute-solvent forces; endothermic
Formation of a Saturated Solution
What is a Saturated Solution
- Maximum amount of solid or gas allowed in a liquid with constant Temperature
Formation of Saturated Solution
How temperature affects saturation
- Increased ==> Increased in solids
- Opposite in gases
Formation of Saturated Solution
Henry’s Law
- Increased Solubility = Increased Pressure
- s = P * k
Formation of Saturated Solution
K in Henry’s Law
- Units: mg[gas]/100g[H2O]/atm
Colligative vs Noncolligative Properties
What are Colligative Properties?
- Physical Properties that depends only on concentration of solute particles, not their identity
- Decreased solvent vapor pressure, Freezing Point Depression, Boiling Point Elevation
Colligative vs Noncolligative Properties
Examples of Noncolligative Properties
- Color, odor, etc.
Volatile Solvents
What if solute is non-volatile?
- Lower solvent volatility because less on surface
- Raoult’s Law: Vapor Psolv = Xsolv ·P°solv
Volatile Solvents
What if solute is volatile?
- Have to consider both Vapor Pressures
- Pressure[Tot] = P[solvent A] + P[solvent B]
= (XsolvA · P°solvA) + (XsolvB · P°solvB)
Fractional Distillation
How does Fractional Distillation work?
- Boil 2 liquids
- Lower Boiling Point will boil out
- Rise to the condenser
- distillate
* Example: Water(50mL) + Ethanol(50mL) = mixture (< 100mL)- Distillation = 50 mL each again
