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Chemistry Module 4 > Alkanes > Flashcards

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

A

UV light

25
Q

What are the types of steps in free radical substitution

A

Initiation, Propagation, Termination

26
Q

What is formed as a result of Homolytic fission

A

2 radicals

27
Q

What is a radical

A

an unpaired atom

28
Q

How reactive are radicals

A

extremley

29
Q

What happens in the initiation step in a free radical substitution

A

The halogen-halogen bond breaks

30
Q

What happens in the termination step

A

2 radicals react ending the whole process

31
Q

What are the 2 main limitations of free radical substitution

A

Further substitution can occur or the halogen can be substituted at different positions

32
Q

How do further substitutions occur in free radical substitution

A

A halogen radical can hit another hydrogen out of a molecule forming a hydrogen radical

33
Q

How is a sigma bond positioned

A

on a line exactly between the 2 atoms

34
Q

what shape does a carbon atom and its hydrogen atoms form

A

3D Tetrahedral shape

35
Q

What state do London forces work in

A

solid and liquid

36
Q

what holds alkanes together in liquid and gases

A

weak London forces

Chemistry Module 4 (8 decks)

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