Alkanes Flashcards
trends down the group?
increase in melting, boiling point
increase in density
increase in viscosity
decrease in flammability
what chemical reactions do alkanes undergo?
Combustion
Cracking
Substitution (Chlorine)
why does melting and boiling point increase down the series?
molecular size increases
resulting in the increase of intermolecular forces between bigger alkane molecules
more heat energy is needed to overcome the stronger intermolecular forces of attraction
why does density increase down the series
molecular size increases
why does viscosity increase down the series
there are stronger intermolecular forces of attraction between alkane molecules as the alkane molecules become bigger thus making it more difficult for liquid to flow
why does flammability decrease down the series
as the molecular size of the alkane increases. the percentage of carbon in alkane molecules increase.
more oxygen is needed to achieve complete combustion of alkane molecules.
such alkanes produces a smokier flame due to incomplete combustion of alkane molecules
what is catalytic cracking?
process whereby large alkane molecules are converted into smaller and more useful molecules using catalysts like aluminium oxide or silicon oxide
what are the uses of catalytic cracking
to obtain hydrogen gas
to obtain smaller and more useful products of alkanes and alkenes
what are the conditions required for cracking?
high temperature of 600*c and the presence of either aluminium oxide or silicon oxide
requirements for substitution reaction
uv light
general formula of alkanes
Cn H2n+2
