Exam I Flashcards
What can we assume from the presence of a lone pair in a molecule?
There will be an unequal distribution of polarity, which will make the molecule behave in an unique way.
What are intramolecular forces?
They are forces within a molecule. Examples are ionic, and covalent.
What are intermolecular forces?
They are forces between molecules. Examples are London forces (dispersion), dipole-dipole, and Hydrogen bonding.
Where can we find dispersion forces?
All molecules
Where can we find dipole-dipole forces?
They are found in all polar molecules, which will present higher BP and MM than molecules of similar MM that are not polar
Where can we find hydrogen bonds?
In all polar molecules with H bonds to F, O, and N. It is basically a dipole-dipole, but generally stronger
Dipole-dipole is the strongest force.
False; it is hydrogen bonding. However dipole-dipole is still strong, as they are permanent
Intermolecular forces only exist between molecules with ionic bounds.
False. Intermolecular forces exist between all substances
Intermolecular forces will ___________ properties of a substance such as _____________, ______________, _____________, and others.
Dictate, boiling point, freezing point, vapor pressure
How do gases, liquids, and solids differ?
In the freedom of movement of their constituent parts.
What is the direction of energy when a phase changes from solid to gas?
Endothermic
What is the direction of energy when a phase changes from gas to solid?
Exothermic
Intermolecular forces determine ________ energy is released or absorbed (defined by ______)
How much, delta H
The stronger the IMF, the lower the temperature needed to overcome them.
False. The higher the temperature has to be in order to overcome them.
What are the main differences between a crystalline and an amorphous substance?
Crystalline substances are regular, ordered, and have a long-term pattern; amorphous substances are still compact but without the long term order.
Intermolecular forces are ________ in nature
Attractive
Every substance will experience some level of dispersion forces; they are called _____________ or temporary, because they can be ________.
Instantaneous; induced
The magnitude of the dispersion forces is a result of…
How easily the substance can be polarized
The strenght of the IMF also depends on the surface area, therefore as branch reduces, IMF reduces as well.
False. As branching increases, IMF reduces
What can we assume from the presence of dipole-dipole forces?
That the positive end of one molecule is attracted to the negative end of the other.
Because dipole-dipole represents a shift in the electron density within a substance…
There will be an e rich region and an e poor region in that molecule. The more the IMF increases, the more the dipole moment increases as well.
What is miscibility?
It is the ability that one substance has to dissolve like substances.
When do we see hydrogen bonding?
In polar molecules where H is connected DIRECTLY to O, F, and N. Therefore, if hydrogen is bonding to a carbon that is bondind to an oxygen, it is not hydrogen bonding.
What is the order of the IMF’s in order of strenght?
Dispersion forces - Dipole-dipole - Hydrogen bonding
Molecules that have hydrogen bonding have generally lower boiling points
False. They have higher boiling points because the attraction between the molecules is high, therefore it requires more energy to separate them.
What molecule has all three types of IMF’s?
Water
When can we find ion-dipole forces?
These forces are present when ions interact with molecular substances
What is surface tension?
It is the energy needed to increase the surface area of a liquid.
Surface tension cannot be altered
False. Surface tension can be altered by adding other substances into the liquid like soap for example.
What is viscosity?
It is the resistance of a liquid to a flow. Generally, the higher the IMF, the higher the viscosity. Viscosity can be affected by the molecular shape, branching, or temperature
What is capillary rise?
It is the natural behavior of a liquid raising on a column; it explains the meniscus shape we see when measuring liquids in a lab.
What are adhesive forces?
They lead unlike substances to stick together
What are cohesive forces?
They lead like substances to stick together.
In H20, ____________ are stronger than ___________; in Hg, ____________ are weaker than ______________.
Adhesive, cohesive, adhesive, cohesive
Phases changes occur during peaks of temperature.
False; phase changes occur at a constant temperature. The energy during a phase change is put in the transition between the phases instead of being used to change the temperature.
What is the heat of vaporization?
Amount of heat required to vaporize 1 mole of a substance. The formula reads Delta H vaporization = - Delta H condensation. Delta H vaporization is endothermic, and delta H condensation is exothermic.
Rate of evaporation = rate of condensation (dynamic equilibrium)
Vapor pressure
Which state of matter is compressible?
Gas
Transition between liquid and solid can also be induced by what?
Changes in pressure
Gases can be condensed by…
Decreasing temperature or increasing pressure
Which halogen has the highest boiling point?
I2
What alcohol also presents all three IMF’s?
Ethanol
The weaker the attractive forces, the higher the vapor pressure.
True
What is the relationship between external pressure and boiling point?
They are directly related; the lower the external pressure, the lower the boiling point.
What is the temperature required to produce a supercritical fluid?
Critical temperature
What is the pressure at the critical temperature called?
Critical pressure
Vaporization is an ______________ process, therefore it is ___________, while condensation is an ______________ process, therefore, it is _____________.
Endothermic, positive, exothermic, negative
Cappilary action involves adhesive and cohesive forces
True
Viscosity of a liquid ___________ as the temperature increases
Decreases
When adding a solute to a solution, no changes are noticed in the properties of the solution.
False; the interferences decreases the freezing point and increases the boiling point
A colligative property depends on the identity of the solute
False. It depends on the concentration of the solute and not on its identity
The boiling point of a siolution is __________ than the pure solvent, and its freezing point is _______________ than the pure solvent.
Higher, lower
What state of matter is held together with relatively high IMF’s?
Solid
In the polar substance CH2O, what IMF’s are present?
Dispersion, dipole-dipole
How many hidrogen bonds can a single water molecule participate in?
4
What happens if an additional solid solute is added to an unsaturated solution?
The solute goes into solution
What happens if addition solid solute is added to a saturated solution?
The solute remains an undissolved solid
