UCSB CHEM 6AL Final Exam Questions With
Correct Answers
Intermolecular forces and how they affect physical properties | | | | | | |
|/purification techniques: dipole-dipole, electrostatic, hydrogen, ion,
| | | | | |
london, - CORRECT ANSWER✔✔-*dipole-dipole*: polar covalent
| | | | | |
molecules such as aldehydes and ketones. positive and negative end.
| | | | | | | | | |
polar molecules must be close together for force to be significant.
| | | | | | | | | | |
weaker than ion-dipole forces; increase with polarity of molecule.
| | | | | | | | |
*electrostatic*: occur between charged species, cations and anions, and | | | | | | | |
are responsible for very high MP and BP of ionic compounds and metals
| | | | | | | | | | | | |
*hydrogen bonding*: hydrogen atom in a polar bond (NOF). considered
| | | | | | | | | |
a dipole-dipole interaction. quite polar.
| | | | |
*ion-dipole*: interaction betwween a charged ion and apolar molecule.
| | | | | | | | |
cations are attracted to negative end of dipole, and anions are attracted
| | | | | | | | | | | |
to positive end.
| | |
*london dispersion*: dependent on surface area and polarizability of
| | | | | | | | |
the surface of the molecule. only types of forces NON-polar covalent
| | | | | | | | | | |
molecules can experience. result from the movement of electrons in the
| | | | | | | | | |
molecule, which generates temporary positive and negative regions in
| | | | | | | | | |
the molecule.
|
,melting point and melting point range - CORRECT ANSWER✔✔-solid has
| | | | | | | | |
ordered crystal lattice structure. heat makes this structure move
| | | | | | | | | |
enough to the point where it becomes a liquid. The melting point is how
| | | | | | | | | | | | |
much energy it takes to make this lattice structre move. Impurities
| | | | | | | | | | | |
disrupt the crystal lattice, so impurities make a structure easier to melt.
| | | | | | | | | | | |
MP also broadens when a compound is impure. If there is water in the
| | | | | | | | | | | | | |
solid, it is impure. solid will stick to side of capillary if still wet. If you
| | | | | | | | | | | | | | | |
dont know the MP range, take a quick measurement to get a rough
| | | | | | | | | | | | |
estimate, then take a second, more careful measurement.
| | | | | | |
limiting reagents and percent yields - CORRECT ANSWER✔✔-*limiting
| | | | | | | |
reagents*: the compound that runs out first. when limiting reagent runs
| | | | | | | | | |
|out, reaction can no longer proceed and other compound is considered
| | | | | | | | | | |
in excess. tell which is limiting reagent by converting grams or mg used
| | | | | | | | | | | | |
to moles using molar mass. when you have moles, use the stoichimetric
| | | | | | | | | | | |
ratios to see which is the smaller amount of moles (mole of reagent
| | | | | | | | | | | | |
under mole produced of product); this is your limiting reagent. could
| | | | | | | | | | |
also compare mole ratios between reagents to see how much you
| | | | | | | | | | |
would need of the other reagent to make reaction go to completion. use
| | | | | | | | | | | |
|limiting reagent to see how much product we will get.
| | | | | | | | | |
*percent yield*: actual yield/theoretical yield X 100. If you expect 10 g
| | | | | | | | | | | |
but only get 8.4, your % yield is 84%. get theoretical yield by taking
| | | | | | | | | | | | | |
limiting reagent and seeing how much product can be made by LR.
| | | | | | | | | | | |
convert g to mol of LR, then convert mol of LR to mol of product; use
| | | | | | | | | | | | | | | |
molar ratio for this. then convert the mol of product by multiplying
| | | | | | | | | | | |
molar mass of product. | | |
, distillation: ideal liquids/Raoults law - CORRECT ANSWER✔✔-*ideal
| | | | | | |
liquid*: a liquid that in incompressible (density is constant), irrotational
| | | | | | | | | |
(no turbulence, flow is smooth), and nonviscous (fulid has no internal
| | | | | | | | | | |
friction). they do not exist in nature. it obeys Raoult's law for all
| | | | | | | | | | | | |
compisitions. |
*Rauoults Law*: shown in picture. total pressure can be found by
| | | | | | | | | | |
adding up partial pressure; partial pressure can be found with Raoult's
| | | | | | | | | | |
law. to find mol fraction (Xa), divide mols of A over total moles of
| | | | | | | | | | | | | |
solution.
Example: what is the partial pressure of EtOH (Po=45 kPa, MW= 46.07
| | | | | | | | | | | |
g/mol) if 3.0 g of it is mixe with 3.0 g of unknown (MW= 32.04)? -
| | | | | | | | | | | | | | | |
CORRECT ANSWER✔✔-18.5 |
a compound with high IMF will have a ____ BP than a compound with
| | | | | | | | | | | | | |
low IMF; Imagine a solution of water boiling in a round flask. the vapors
| | | | | | | | | | | | | |
above this liquid are ______ the liquid themselves. - CORRECT
| | | | | | | | | |
ANSWER✔✔-higher; the same temp as | | | |
T or F: higher vp means that a liquid is harder to turn into a vapor -
| | | | | | | | | | | | | | | | |
CORRECT ANSWER✔✔-F its easier!
| | |
Correct Answers
Intermolecular forces and how they affect physical properties | | | | | | |
|/purification techniques: dipole-dipole, electrostatic, hydrogen, ion,
| | | | | |
london, - CORRECT ANSWER✔✔-*dipole-dipole*: polar covalent
| | | | | |
molecules such as aldehydes and ketones. positive and negative end.
| | | | | | | | | |
polar molecules must be close together for force to be significant.
| | | | | | | | | | |
weaker than ion-dipole forces; increase with polarity of molecule.
| | | | | | | | |
*electrostatic*: occur between charged species, cations and anions, and | | | | | | | |
are responsible for very high MP and BP of ionic compounds and metals
| | | | | | | | | | | | |
*hydrogen bonding*: hydrogen atom in a polar bond (NOF). considered
| | | | | | | | | |
a dipole-dipole interaction. quite polar.
| | | | |
*ion-dipole*: interaction betwween a charged ion and apolar molecule.
| | | | | | | | |
cations are attracted to negative end of dipole, and anions are attracted
| | | | | | | | | | | |
to positive end.
| | |
*london dispersion*: dependent on surface area and polarizability of
| | | | | | | | |
the surface of the molecule. only types of forces NON-polar covalent
| | | | | | | | | | |
molecules can experience. result from the movement of electrons in the
| | | | | | | | | |
molecule, which generates temporary positive and negative regions in
| | | | | | | | | |
the molecule.
|
,melting point and melting point range - CORRECT ANSWER✔✔-solid has
| | | | | | | | |
ordered crystal lattice structure. heat makes this structure move
| | | | | | | | | |
enough to the point where it becomes a liquid. The melting point is how
| | | | | | | | | | | | |
much energy it takes to make this lattice structre move. Impurities
| | | | | | | | | | | |
disrupt the crystal lattice, so impurities make a structure easier to melt.
| | | | | | | | | | | |
MP also broadens when a compound is impure. If there is water in the
| | | | | | | | | | | | | |
solid, it is impure. solid will stick to side of capillary if still wet. If you
| | | | | | | | | | | | | | | |
dont know the MP range, take a quick measurement to get a rough
| | | | | | | | | | | | |
estimate, then take a second, more careful measurement.
| | | | | | |
limiting reagents and percent yields - CORRECT ANSWER✔✔-*limiting
| | | | | | | |
reagents*: the compound that runs out first. when limiting reagent runs
| | | | | | | | | |
|out, reaction can no longer proceed and other compound is considered
| | | | | | | | | | |
in excess. tell which is limiting reagent by converting grams or mg used
| | | | | | | | | | | | |
to moles using molar mass. when you have moles, use the stoichimetric
| | | | | | | | | | | |
ratios to see which is the smaller amount of moles (mole of reagent
| | | | | | | | | | | | |
under mole produced of product); this is your limiting reagent. could
| | | | | | | | | | |
also compare mole ratios between reagents to see how much you
| | | | | | | | | | |
would need of the other reagent to make reaction go to completion. use
| | | | | | | | | | | |
|limiting reagent to see how much product we will get.
| | | | | | | | | |
*percent yield*: actual yield/theoretical yield X 100. If you expect 10 g
| | | | | | | | | | | |
but only get 8.4, your % yield is 84%. get theoretical yield by taking
| | | | | | | | | | | | | |
limiting reagent and seeing how much product can be made by LR.
| | | | | | | | | | | |
convert g to mol of LR, then convert mol of LR to mol of product; use
| | | | | | | | | | | | | | | |
molar ratio for this. then convert the mol of product by multiplying
| | | | | | | | | | | |
molar mass of product. | | |
, distillation: ideal liquids/Raoults law - CORRECT ANSWER✔✔-*ideal
| | | | | | |
liquid*: a liquid that in incompressible (density is constant), irrotational
| | | | | | | | | |
(no turbulence, flow is smooth), and nonviscous (fulid has no internal
| | | | | | | | | | |
friction). they do not exist in nature. it obeys Raoult's law for all
| | | | | | | | | | | | |
compisitions. |
*Rauoults Law*: shown in picture. total pressure can be found by
| | | | | | | | | | |
adding up partial pressure; partial pressure can be found with Raoult's
| | | | | | | | | | |
law. to find mol fraction (Xa), divide mols of A over total moles of
| | | | | | | | | | | | | |
solution.
Example: what is the partial pressure of EtOH (Po=45 kPa, MW= 46.07
| | | | | | | | | | | |
g/mol) if 3.0 g of it is mixe with 3.0 g of unknown (MW= 32.04)? -
| | | | | | | | | | | | | | | |
CORRECT ANSWER✔✔-18.5 |
a compound with high IMF will have a ____ BP than a compound with
| | | | | | | | | | | | | |
low IMF; Imagine a solution of water boiling in a round flask. the vapors
| | | | | | | | | | | | | |
above this liquid are ______ the liquid themselves. - CORRECT
| | | | | | | | | |
ANSWER✔✔-higher; the same temp as | | | |
T or F: higher vp means that a liquid is harder to turn into a vapor -
| | | | | | | | | | | | | | | | |
CORRECT ANSWER✔✔-F its easier!
| | |
