Chemistry Final Flashcards

Intermolecular Forces (IMFs)

• IMFs are attractive forces between atoms and molecules due to electrostatic phenomena.

Boiling Points of Compounds

• Order of compounds from lowest to highest boiling point: CH₄ < SiH₄ < GeH₄ < SnH₄.
• Compounds are nonpolar and experience dispersion forces; larger molecules lead to stronger dispersion.

Hydrocarbons Boiling Points

• Order for hydrocarbons from lowest to highest boiling point: C₂H₆ < C₃H₈ < C₄H₁₀.
• All hydrocarbons are nonpolar with London dispersion forces; boiling points increase with molecular size.

Dipole-Dipole Attraction

• Occurs between the partially positive end of one polar molecule and the partially negative end of another.
• Only polar molecules exhibit this attraction.

Comparison of N₂ and CO

• CO has a higher boiling point due to its polarity and dipole-dipole attractions.
• Both have the same mass but CO’s dipole forces are stronger than N₂'s dispersion forces.

Hydrogen Bonding

• A strong dipole-dipole attraction occurs when hydrogen is bonded to fluorine, oxygen, or nitrogen.
• Large electronegativity differences and small size of hydrogen lead to concentrated partial charges.

Strength of Hydrogen Bonds

• Hydrogen bonds are about 5-10% as strong as covalent bonds but are stronger than other dipole-dipole attractions and dispersion forces.

Boiling Points of Dimethyl Ether, Ethanol, and Propane

• IMFs strength order: Propane (only dispersion forces) < Dimethyl Ether (dipole-dipole) < Ethanol (hydrogen bonding).
• Boiling points: Propane: -42.1 °C, Dimethyl Ether: -24.8 °C, Ethanol: 78.4 °C.

Viscosity

• Defined as a liquid's resistance to flow; stronger IMFs result in greater viscosity.

Cohesive Forces

• IMFs existing between identical molecules of a substance contribute to liquid surface behavior.

Surface Tension

• Energy required to increase the surface area of a liquid, caused by cohesive forces at the liquid's surface.

Capillary Action

• Phenomenon where liquid flows in porous materials due to molecular attraction to the surface and themselves.

Phase Changes

• Condensation involves the transition from gas to liquid.
• Vaporization refers to the change from liquid to gas.

Dynamic Equilibrium

• A condition where vaporization and condensation processes occur at identical rates.

Vapor Pressure

• Maximum vapor pressure of a liquid at a given temperature; it remains constant if the temperature is stable.

Boiling Point Definition

• The temperature at which a liquid's vapor pressure equals the applied external pressure.

Normal Boiling Point

• Boiling point at an external pressure of 1 atm (101.3 kPa).

ΔH of Vaporization for Water

• Energy required to convert one mole of liquid water to vapor: 40.7 kJ/mol.

Specific Heat of Water

• Specific heat values: solid H₂O: 37.6 kJ/mol, liquid H₂O: 75.1 kJ/mol, gaseous water vapor: 33.1 kJ/mol.

ΔH of Fusion for Water

• Energy needed to convert one mole of liquid water to solid: ΔH (fus) H₂O > 0, 6.02 kJ/mol.

Sublimation of Water

• Energy required to convert solid water to gas, skipping the liquid phase: ΔHsub = ΔHfus + ΔHvap, ΔHsub > 0.

ΔHdep

• Energy required to convert one mole of water vapor directly into solid ice: ΔHdep < 0, ΔHdep = -ΔHsub.