4.1.2 Alkanes Flashcards
(20 cards)
general formula of an alkane
CnH2n+2
what is the general formula of a cyclo alkane
CnH2n
what is the shape and bond angle of alkanes
tetrahedral, 109
what are sigma bonds
sigma bonds are formed by the direct overlap of orbitals directly between atoms
what intermolecular forces arise between alkanes
induced dipole - dipole forces
why does an alkanes boiling point increase the longer the carbon chain is
larger molecules have greater surface contact and therefore greater induced dipole dipole interactions. More energy is required to overcome these forces and separate the molecules so the boiling point is therefore higher
why do straight chained alkanes have a high boiling point than branched chains
surface contact in branched chain molecules is less, the molecules cannot get as close together therefore there is less attractive forces meaning induced dipole - dipole interactions are easier to overcome
why is it inappropriate to use a line of best fit on alkane boiling point graphs
the number of carbon atoms is a discrete variable.
Each molecule cannot have a fraction of a carbon atom.
what is room temperature in degrees and kelvin
25 degrees 298K
what kind of reaction is combustion
exothermic
what are the products of complete combustion with a plentiful supply of oxygen
CO2 + H2O
what are the products of incomplete combustion with a limited supply of oxygen
CO + H2O
when do alkanes react with halogens
in the presence of UV light
what happens when a covalent bond is broken homolytically
a hydrogen atom on the alkane is substituted for a halogen atom
what is formed when a hydrogen atom is replaced for a halogen atom
free radical
why are free radicals highly reactive
the contain and unpaired electron
what are the 3 steps in halogenation
- initiation
- propagation
- termination
what is the mechanism called for halogenation
free radical substitution
what is the reaction called that causes a bond to break due to the absorption of light
photochemical reaction
why is CO dangerous
haemoglobin is carried by red blood cells. Bonding between oxygen and haemoglobin is weak. However, bonding between CO and haemoglobin is stronger and irreversible. Therefore, oxygen is replaced with CO and normal cell respiration is blocked. Eventually leading to death
