alkanes and alkenes

Question 1

alkane

Answer 1

saturated hydrocarbon
formula: CnH2n+2

Question 2

what happens moving down the alkane series

Answer 2

the molecular size increases which means the intermolecular forces of attraction becomes stronger which will increasing melting and boiling point and viscosity. the flammability will decrease

Question 3

chemical properties of alkane

Answer 3

unreactive due to strong c-c bond causing diffult to break
they can only undergo combustion or substitution
combustion occurs when an alkane combines with oxygen to produce water and carbon dioxide
substitution with halogen (at least one hydrogen is replaced by halogen atom)

Question 4

alkene

Answer 4

unsaturated hydrocarbons
CnH2n

Question 5

chemical properties of alkene

Answer 5

undergo complete combustion when there is sufficient oxygen to form water and carbon dioxide
undergo incomplete combustion to form soot and carbon monoxide

unsaturated compound due to presence of C=C bond -> undergo addition

Question 6

how is margarine produced?

Answer 6

margarine is produced by adding hydrogen to vegetable oil as it is polyunsaturated and there are many C=C bonds

Question 7

cracking

Answer 7

large hydrocarbons can be broken down into smaller molecules through cracking

Question 8

physical properties of alkanes and alkenes

Answer 8

low melting an boiling point
soluble in organic solvent
insoluble in water

Question 9

catalysts and temperature for addition reaction

Answer 9

nickel
200dc

Question 10

test for alkane and alkene

Answer 10

add reddish-brown aqueous bromine solution
observation
alkane: remains reddish-brown
alkene: becomes colourless

Question 11

how to obtain pure crystals

Answer 11

Heat the solution till saturated. Allow it to cool and crystallize. Filter the mixture to obtain crystals. Rinse with distilled water and dry with filter paper