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chem pr

Terms

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substance present in the small proportion in a solution
solute
substance present in the greatestproportion in a solution
solvent
process that occurs when the solvent molecules surround the solute molecules
solvation
if the solvent is water for solvation, what is the process called?
hydration
(t/f) solutions can involve any of the three phases of matter
true. can have a solution of two gases, solid in a solid (alloy), solid in a liquid, etc.
what is a solid in a solid solution called?
an alloy.
when a solution has water as the solvent, what kind of solution is it called?
aqueous
what is a saturated solution?
one in which no more solute will dissolve; at this point we have reached the molar solubility of the solute for that particular solvent.
what is the reverse process of dissolution
precipitation;
occurs at the same rate as dissolving; both the solid form and the dissolved form are said to be in dynamic equilibrium.
solubility
refers to the amnt of solute that will saturate a particular solvent.
(T/F) Solubility is specific for the type of solute and solvent.
True.
(T/F) Solubility varies with temperature, increasing or decreasing with temperature depending upon the solute and solvent.
True;
The solubility of most solids in liquids (increase/decrease) with increasing temperature.
True.
The solubility of most gases in liquids (increases/decreases) with increasing temperature.
decreases
Molarity (M)
(# of moles of solute) / (# liters of solution)
Electrolytes
free ions in a solution;
called this b/c the solution can conduct electricity.
strong electrolytes vs. weak electrolytes vs. non-electrolytes
- strong: dissociate completely
- weak: remain ion-paired.
- non-electrolytes: covalent compounds that don't dissociate into ions.
(T/F) Solutions of strong electrolytes are better conductors ofe lectricity those of weak electrolytes.
True.
van't Hoff(or ionizability) factor
tells us how many ions one unit of a substance will produce in solution.
What is the van't Hoff factor of C6H12O6?
it's non-ionic so it doesn't dissociate; thereby, i =1.
What is the van't Hoff factor for almost all biomolecules -- hormones, proteins, steroids, etc.?
1
What is the Van't Hoff Factor of NaCl?
It dissociates into Na+ and Cl-; therefore, i=2.
What is the Van't Hoff Factor of HNO3?
this dissociates into H+ and NO3-; therefore, i=2.
What is the Van't Hoff Factor of CaCl2?
It dissociates into Ca2+ and 2Cl-; therefore i=3.
Covalent Bond
formed btw atoms when each contributes one of itsunpaired valence electrons.
(T/F) Electrons in d subshells are not considered valence electrons when writing Lewis dot symbols.
True.
What will tell you if the atoms are sharing their electrons in the "best" way possible?
- the formal charge (the best structure is the one that minimizes the magnitude of the formal charges.)
Formal charge formula
V-0.5B-L where V is the number of valence electrons, B is the number of bonding electrons, and L is the number of lone pair (non-bonding electrons).
What should you do first whenever trying to see what the best Lewis structure is?
Simply count up all the electrons and see if it matches.
(T/F) Resonance structures are two or more sturcutres where only nonbonding electrons, and double and triple bonds may move around.
True.
polarity
molecule is partially negative (denoted by delta negative) and partially positive (denoted by delta positive)
A bond is polar if...
- the electron density between the two nuclei is uneven;
- if there is a different in electronegativity.
Is CCl4 polar or nonpolar?
Its non-polar because the four polar bonds are symmetrically arranged leaving the molecules as a whole nonpolar, with no dipole moment.
Is O=C=S polar?
Yes; although C=O is more polar than the C=S giving a net dipole moment in the C=O direction.
Coordinate covalent bond
when one attom donates both of the shared electrons in a bond; such as the lone pair on boron of NH3.
Lewis base
aka. ligand
electron pair donator. (SUch as NH3)
Lewis Acid
electron pair acceptor; such as BF3
Whcih one of the following anions cannot behave as a Lewis base/ligand?
a. F-
b. OH-
c. NO3-
d. BH4-
Must have a pair of nonbonding electrons to be a candidate Lewis base/ligand ==> choice D doesn't have any nonbonding electrons.
(T/F) Carbon atoms with nonbonding electrons are excellent Lewis bases/ligands.
True;
Ie. CO, -CN, and -CH3 are all good lewis bases while CO2 is not.
For an ionic bond to form btw a metal and a non-metal, what has to be pressent?
a big difference in electronegativity between the two elements.
Which is stronger ionic bond: MgO or NaCl?
- For MgO, we have PE prop (+2)(-2)/r while for NaCl we have PE prop (+1)(-1)/r.
- Note that these PE are negative ==> ionic system is more stable than the ions separated from each other.
- Ratio of these potential energies is -4/-1=4
(T/F) Hydrogen is considered an alkali metal.
- False!
- hydrogen itself is not considered to be one of the alkali metals. Its place in the table does make sense, though; hydrogen tends to behave like the other members of its column in chemical reactions. For example, all these elements combine with oxygen to form compounds with the formula X2O.

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