CHEM 112 Flashcards
Gen Chem II
intermolecular forces
weak attractions between SEPARATE molecules that hold them together; NOT bonds
types of IMF in order of increasing strength
dispersion, dipole-dipole, hydrogen-bonding, ion dipole
What IMF is present in all molecules?
dispersion forces
dipole-dipole forces
occur due to unequal sharing of electrons (polar molecules)
Dispersion forces are the only IMF present in ________ molecules
nonpolar
How does hydrogen-bonding work?
Can only form between a lone pair on N, O, or F in one polar molecule and an H bonded to N, O, or F in another polar molecule
ion-dipole
strongest IMF, occurs between ionic compounds
Which is the better solvent for NaCl and why? CH3OH or CH3(CH2)5OH
CH3OH- has fewer hydrocarbons
the other molecule is too nonpolar, so it cannot dissolve ionic compounds as well
Why do ionic compounds have high conductivity? What about acids?
They dissociate in water, allowing CHARGED ions to move freely
How and why does the presence of solute change the vapor pressure and boiling point of a solution as opposed to a pure solvent?
VP decreases, BP increases because solute particles block gas escape
Which has a higher conductivity, KNO3 or CaBr2
CaBr2 has more ions (1 Ca and 2 Br), KNO3 has 1 K and 1 nitrate
What does Tf represent?
freezing point
What is the formula for molar ratio?
X = mol component/total mol
What is the formula for molality?
m = mol solute/kg solvent
What is the formula for Vant Hoff?
i = mol particle/mol solute
What is the van’t Hoff factor?
shows how solutes affect colligative properties of solutions
What is the van’t Hoff factor of a covalent compound?
i = 1
What is the van’t Hoff factor of an ionic compound or acid?
i = number of particles in compound (ex: HNO3 i = 2, 1 hydrogen, 1 nitrate)
intramolecular forces
attractions between atoms WITHIN in a molecule that keep them bonded together
covalent bonds vs. IMFs
- covalent bonds share electrons to create strong INTRAmolecular forces inside a molecule; are not broken by phase changes
- INTERmolecular forces create attractions between SEPARATE molecules and CAN be broken by phase changes
van der Waals forces
collective term for dispersion, dipole-dipole, and hydrogen bonding
The higher the mass of a compound, the _____ its boiling point
higher, larger molecules generally have more IMFs so more heat is needed to disrupt and cause liquid —> gas change
The stronger the IMFs of a compound, the _____ its boiling point
higher; need more heat to disrupt IMFs and allow vaporization
