Chemistry Final Flashcards

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Questions and Answers

What are intermolecular forces (IMFs)?

The various forces of attraction that may exist between the atoms and molecules of a substance due to electrostatic phenomena

Order the following compounds of a group 14 element and hydrogen from lowest to highest boiling point: CH₄, SiH₄, GeH₄, and SnH₄.

CH₄ < SiH₄ < GeH₄ < SnH₄

Order the following hydrocarbons from lowest to highest boiling point: C₂H₆, C₃H₈, and C₄H₁₀.

C₂H₆ < C₃H₈ < C₄H₁₀

What is dipole-dipole attraction?

The electrostatic forces of attraction between the partially positive end of one polar molecule and the partial negative end of another polar molecule. Signup and view all the answers

Which has the higher boiling point: N₂ or CO?

CO Signup and view all the answers

What is hydrogen bonding?

A particularly strong dipole-dipole attraction that occurs when a molecule contains a hydrogen atom bonded to a fluorine, oxygen, or nitrogen atom. Signup and view all the answers

Hydrogen bonds are much weaker than covalent bonds.

True Signup and view all the answers

Match the following compounds with their boiling points: dimethylether (CH₃OCH₃), ethanol (CH₃CH₂OH), and propane (CH₃CH₂CH₃)

dimethylether (CH₃OCH₃) = -24.8 °C ethanol (CH₃CH₂OH) = 78.4 °C propane (CH₃CH₂CH₃) = -42.1 °C Signup and view all the answers

What is viscosity?

A liquid's resistance to flow, related to the strength of intermolecular forces. Signup and view all the answers

What are cohesive forces?

The various intermolecular forces between identical molecules of a substance. Signup and view all the answers

What is surface tension?

The energy required to increase the surface area of a liquid, caused by cohesive forces. Signup and view all the answers

What is capillary action?

When a liquid flows within a porous material due to the attraction of the liquid molecules to the surface of the material and to other liquid molecules. Signup and view all the answers

What is condensation?

The change from the gas phase to the liquid phase. Signup and view all the answers

What is vaporization?

The change from the liquid phase to the gas phase. Signup and view all the answers

What is dynamic equilibrium?

The status of a system in which reciprocal processes occur at equal rates. Signup and view all the answers

What is vapor pressure?

The maximum vapor pressure of a liquid at a given temperature, remaining constant at constant temperature. Signup and view all the answers

What is boiling point?

The temperature at which the liquid's vapor pressure is equal to the applied external pressure. Signup and view all the answers

What is normal boiling point?

Its boiling point when surrounding pressure is equal to 1 atm (101.3 kPa) Signup and view all the answers

What is the ∆H of vaporization for water?

40.7 kJ per mole Signup and view all the answers

What does ∆H represent in thermodynamics?

Change in enthalpy. Signup and view all the answers

What is C_s (specific heat of solid H₂O)?

37.6 kJ/mol Signup and view all the answers

What is C_l (specific heat of liquid H₂O)?

75.1 kJ/mol Signup and view all the answers

What is C_g (specific heat of gaseous water vapor)?

33.1 kJ/mol Signup and view all the answers

What is the ∆H of fusion for water?

6.02 kJ/mol Signup and view all the answers

What is ∆Hsub of H₂O?

∆Hsub = ∆Hfus + ∆Hvap Signup and view all the answers

What is the ∆Hdep?

Amount of energy required to convert one mole of water vapor directly into solid ice. Signup and view all the answers

Study Notes

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.

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Description

Review key concepts in chemistry with these flashcards, focusing on intermolecular forces and boiling points of compounds from group 14. Perfect for preparing for your chemistry final exam.