Properties of Alkanes Flashcards
Are alkanes saturated or unsaturated hydrocarbons?
Saturated -they only have s single ‘C-C’ bond
Name the shape of the bond around each carbon atom in alkanes
Tetrahedral shape
Give the bond angle around each carbon atom in alkanes
109.5 degrees
Name the type of covalent bond in alkanes
Sigma bonds
What is a sigma bond?
The direct overlap of electron orbitals between bonding atoms
THINK: ‘sigma sigma bond sigma bond sigma bond, direct overlap of (electron) orbitals between bonding atoms!
There is [blank] rotation about sigma bonds
fill in the blank
Free
Sigma bonds are strong.
TRUE or FALSE
TRUE
Are alkanes soluble in water?
No
Why are alkanes insoluble in water
They are non-polar and so don’t have permanent dipoles and so cannot form hydrogen bonds with water molecules
Explain why longer chain alkanes have a higher boiling point
- All alkanes experience London Forces
- As the number of carbon chains increases, the strength of the London Forces increases
- This is becauselonger chain alkanes have more elctrons and a greater surface area which means more points of contact, both of which increase the strength of London forces
Does boiling point increase or decrease as alkanes increase in chain length
Increase
Which one has the higher boiling point, a straight chain alkane or a branched alkane?
Straight chain alkane
Does branching cause the boiling point of alkanes to increase or decrease?
Decrease
Why does branching cause the boiling points of alkanes to reduce?
- Branching prevents alkanes molecules from getting closer to eachother
- This lowers the boiling point as London forces work the strongest over short distances and so London forces are reduces
