5條chem既問題

1.
heating can be with or without air. if a reaction requires vacuum / inert atmosphere / oxygen-free, it'll specify.
if not specified, it's reasonable to assume it to be heated under air. check if any reactant could react with air (oxygen or nitrogen).


2.
fluorine has 3 lone pairs, but every HF molecule has only 1 hydrogen (lone-pair acceptor).
it's possible to form 3 H-bond with one F-atom, but on average, 1 HF molecule forms 1 H-bond
(2 when you consider an H-bond from hydrogen and another H-bond from F-atom.)


3.
the molecule is bent at oxygen atom, yielding non-zero vector sum of the dipole moment. thus it's polar.
the O-atom has lone-pair, ready to donate to form H-bond. however, there're no lone-pair acceptor (i.e. H-atom attached on a highly electronegative atom). donor without acceptor can't yield H-bond.


4.
so are you comparing m.p OR b.p. ??
packing efficiency is one of the factors affecting melting point, but not all.
boiling point mainly depends on strength of intermolecular force, so your statement SHOULD be correct.


5.
consider there're bundles on carbon nanotubes. when the tubes come together, the p-orbitals on the surface of the tubes overlap, allowing electrons to flow through.
electrons aren't necessary to flow within same molecule.
consider graphite: the sheets of carbon are not infinite, yet it can conduct electricity ---- overlapping of p-orbitals on the sheet-like structure.