Alkanes Flashcards

1
Q

What are alkanes the main component of?

A

Natural Gas

Crude Oil

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2
Q

What is the general formula of alkanes?

A

C(n)H(2n+2)

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3
Q

What is a sigma bond?

A

The result of the overlap of two orbitals, one from each bonding atom, with each overlapping orbital containing one electron.

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4
Q

What is the shape and bond angle around each carbon in an alkane?

A

Tetrahedral, 109.5

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5
Q

Are sigma bonds rigid?

A

No, rotation around atom is free and movement can occur

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6
Q

How does fractional distillation work?

A

Separation by boiling points, different alkanes of different chain lengths have different boiling points so can be separated

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7
Q

How does boiling point change as chain length changes?

A
Increases
Larger surface area
Greater surface area of contact
London forces greater
Requires more energy to overcome
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8
Q

What affect does branching have on boiling point?

A

Decreases boiling point
Fewer surface area points of contact so fewer London forces
Molecules can’t get as close decreasing intermolecular forces

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9
Q

What are the three reasons for lack of reactivity of the alkanes?

A

Sigma bonds are strong
C-C bonds are non polar
Electronegativity value of C and H are so similar they can be seen to be non-polar

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10
Q

What are the products of complete combustion?

A

Carbon Dioxide and Water

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11
Q

What two products can be formed in incomplete combustion?

A

Carbon Monoxide

Carbon

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12
Q

When do alkanes react with halogens?

A

In the presence of UV light

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13
Q

What are the three steps of radical substitution?

A

Initiation
Propagation
Termination

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14
Q

What happens in the initiation step?

A

The covalent bond in the halogen molecule is broken by homolytic fission
Forms two halogen radicals

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15
Q

Where does the energy come from for homolytic fission in radical substitution?

A

UV light

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16
Q

How many propagation steps are there?

A

2

17
Q

When does a propagation reaction get terminated?

A

When two radicals collide or all reactants are used up

18
Q

What happens in the termination stage?

A

Two radicals collide

Forms a molecule with all electrons paired

19
Q

What are the 2 limitations of radical substitution?

A

Further Substitution

Substitution at different points on the carbon chain