Alkanes Flashcards

1
Q

What is an alkane

A

A saturated hydrocarbon

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2
Q

What type of bonds are formed between atoms in alkanes

A

sigma bonds

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3
Q

What is a sigma bond

A

A bond between 2 atoms formed when 1 orbital from each atom overlaps each other

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4
Q

Why do pairs of electrons repel each other

A

Because sigma bonds between carbon atoms and hydrogen atoms cause a repulsion

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5
Q

What angle is made by atoms in an alkane

A

109.5 degrees

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6
Q

What allows atoms to freely rotate in an alkane

A

Sigma bonds allow rotation to occur as they act as an axes

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7
Q

How is crude oil separated

A

fractional distillation towers

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8
Q

How does a fractional distillation tower separate hydrocarbons from crude oil

A

Crude oil turned into gas and gas enters tower where it rises, temperature changes so different boiling points of hydrocarbons lead to them becoming liquids`

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9
Q

What effect does chain length have on alkanes

A

The longer the chain, the larger the surface area of the molecule meaning more London forces can be formed between the molecules

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10
Q

What are London forces

A

weak intermolecular force

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11
Q

How does branching effect the chain length of alkanes

A

Branching lowers boiling point because the surface area is smaller so London forces don’t form as regularly

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12
Q

How reactive are alkanes with reagents

A

not very

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13
Q

Why are alkanes not very reactive with reagents

A

strong sigma bonds, no polarity mean that alkanes are not very reactive with reagents

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14
Q

Alkanes react really well with _____

A

oxygen

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15
Q

How does combustion occur with alkanes

A

when alkanes meet oxygen

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16
Q

What is released in complete combustion

A

carbon dioxide + water ( + energy )

17
Q

Why are alkanes good fuels

A

They’re readily available, easily transportable, don’t produce any toxic products

18
Q

What is complete combustion

A

when alkanes react with a plentiful supply of oxygen

19
Q

what is incomplete combustion

A

when an alkane reacts with a little supply of oxygen

20
Q

What are the 2 possible products that can from in incomplete combustion

A

soot (solid carbon)

carbon monoxide

21
Q

What is carbon monoxide

A

An odourless, colourless, toxic gas that damages the body

22
Q

Why is carbon monoxide bad for you

A

Because the carbon monoxide combines with oxygen which provides little space for oxygen to be carried around

23
Q

How does an alkane form a haloalkane (mechanism)

A

free radical substitution

24
Q

What is needed to break a halogen-halogen bond

25
What are the types of steps in free radical substitution
Initiation, Propagation, Termination
26
What is formed as a result of Homolytic fission
2 radicals
27
What is a radical
an unpaired atom
28
How reactive are radicals
extremley
29
What happens in the initiation step in a free radical substitution
The halogen-halogen bond breaks
30
What happens in the termination step
2 radicals react ending the whole process
31
What are the 2 main limitations of free radical substitution
Further substitution can occur or the halogen can be substituted at different positions
32
How do further substitutions occur in free radical substitution
A halogen radical can hit another hydrogen out of a molecule forming a hydrogen radical
33
How is a sigma bond positioned
on a line exactly between the 2 atoms
34
what shape does a carbon atom and its hydrogen atoms form
3D Tetrahedral shape
35
What state do London forces work in
solid and liquid
36
what holds alkanes together in liquid and gases
weak London forces