alkanes

Question 1

what are alkanes?

Answer 1

alkanes are saturated organic compounds that contain only single bonds between carbon atoms

Question 2

what is the general formula for alkanes?

Answer 2

CnH2n+2

Question 3

what is methane’s
-full structure bond
-no. of carbon atoms
-molecular formula

Answer 3

1 carbon atom
CH4

Question 4

what is ethane’s
-full structure bond
-no. of carbon atoms
-molecular formula

Answer 4

2 carbon atoms
C2H6

Question 5

what is propane’s
-full structure bond
-no. of carbon atoms
-molecular formula

Answer 5

3 carbon atoms
C4H8

Question 6

what is butane’s
-full structure bond
-no. of carbon atoms
-molecular formula

Answer 6

4 carbon atoms
C4H10

Question 7

what are the physical properties of alkanes?

Answer 7

low melting and boiling point
insoluble in water
soluble in organic solvents

Question 8

what are the changes down the homologous series?

Answer 8

melting and boiling point increase
this is because as the alkane molecule increases, a larger amount of energy is required to overcome the stronger intermolecular forces between the molecules
viscosity increases
this is because as the size of alkane molecule increases, more energy is required to overcome the intermolecular forces between molecules. hence, they flow less easily.
flammability decrease
this is because as the alkane molecule increases,the percentage of carbon in alkane molecules increases. hence, larger alkane molecules are less flammable and produce a smokier flame (due to incomplete combustion)

Question 9

what are the chemical properties of alkanes?

Answer 9

alkanes consist of only single carbon-carbon and carbon-hydrogen bonds. these bonds are strong and difficult to break. hence, alkanes are generally unreactive.
combustion
alkane+excess oxygen->co2+water vapour(complete combustion)
alkane+limited oxygen->co+water vapour(incomplete combustion)
substitution
in the presence of uv light, alkanes can react with halogens, such as chlorine and bromine
if excess halogen is used, more hydrogen atoms can be substituted with halogen atoms