11/17 notes Flashcards
electrons are always what
moving around nucleus
room temperatuer and oressure are what type of conditions
standard
pressure standard =
1 atm
room temp is
25C or 285K
what do all molcuels have
can form alrger and longer lasting temp diploes therefore stronger and attractive forced
forces get stronger with
molcule size
strength of diploes for compact structure
weaker dipoes
where do permanent diopole forces exist
exist in molecules that have net dipoles
is permanebt dipole attraction is stronger than temporary dipole attraction
yes
the larger the net dipole the _____the attraction
stronger
Describe in detail why even nonpolar molecules have attractive intermolecular forces.
because of temporary dipoles that occur in nonpoalr molecules when electrond constantly orbit the nuceus occupy a similar location by chance
why is a temporary dipole called temporary
called temporary dipoles because electronsare always moving
Why do all atoms and molecules have temporary dipole forces?
all atoms have temporary dipoles because electrond are always moving around the nucleus
What factors increase the size of temporary dipole forces? W
the size of tenporary dipole is caused by polarizability: valnce electrons are not held as tightly, can form larger and longer lasting temp dipoles therefore stronger attractive forces
What intermolecular forces do polar molecules have?
permanent dipole IMF
How does the size of the molecule’s dipole impact the strength of the intermolecular force? And
how would this affect its melting and boiling points?
the larger the net dipole the stronger the attraction, the larger the et dipole the hgh the melting and boiling point
What is a hydrogen bond?
exists in molecues with x-h binds where x=N,O,F
-anything with H has a net dipole
How does the strength of hydrogen bonds compare to permanent dipole forces and temporary
dipole forces?
h bonds are stronger than dipole attractions
Why are most small covalent molecules gases at room temperature and pressure? Why might
some of them be liquids?
most small covalent molecule gases are at room temp and pressure b/c IMF of attractio between mokecukes are weak and easy to overcome. Very little energy is required to overcome these forces, therefore simple molecules are liquids + gases at room temp
Why does increasing molecular size increase the boiling point?
b/c IMF of attraction betwewen molecules is stronger and harder to overcome. More energy is required to overcome these forces
Why are most large covalent molecules solids at room temperature and pressure?
moelcules have so many electrons. the resulting dispersion forces between these molecules makes them assume the solid phase at normal temperatures
How do intermolecular forces strengths compare with covalent bond strengths?
IMF forces are genrlly weaer than covalent bonds
(Note that the covalent bond is intramolecular or within a molecule, while intermolecular
attractive forces are between discrete molecules.)
Given a chemical substance, what type of intermolecular forces does it have?
ion dipole forces are positively charged end of a polar molcule such as H2O is attracted to negative ions
