12.1 properties of alkanes

Question 1

what type of covalent bond are in single bonds?

Answer 1

sigma bonds

Question 2

what is a covalent bond?

Answer 2

shared pair of electrons

Question 3

what is a sigma bond a result of?

Answer 3

overlap of 2 orbitals, one from each bonding atom

Question 4

what bond angles are in alkanes?

Answer 4

109.5

Question 5

what is the general formulae of alkanes?

Answer 5

CnH2n+2

Question 6

effect of chain length on boiling point

Answer 6

• longer chains, greater surface points of contact
• stronger London forces
• boiling point increases

Question 7

effect of branching on boiling point

Answer 7

• more chains, fewer surface points of contact
• weaker London forces
• boiling point decreases

Question 8

kerosene is obtained from crude oil. name the process used to obtain kerosene from crude oil and explain how the process works

Answer 8

• fractional distillation
• different fractions in crude oil have different boiling points
• increase the temperature of the system so each fraction vaporises separately from the other fractions ad can be collected

Question 9

describe the bonding in ethane. state and explain the H-C-H bond angle in a molecule of ethane

Answer 9

• single covalent bonds between the C-C and the C-H bods are sigma bonds
• sigma bond is the overlap of orbitals, one from each bonding atom
• each carbon atom is bonded to four other atoms by covalent bonds
• the shape around each carbon atom is tetrahedral
• 4 bonding pairs of electrons repel equally to give a bond angle of 109.5 around the carbon atom

Question 10

what is the shape of alkanes?

Answer 10

tetrahedral