12.1 Properties Of Alkanes Flashcards

1
Q

Alkane general formula

A

CnH2n+2

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2
Q

What are the bonds in alkanes called?

A

Sigma bonds

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3
Q

What is a sigma bond?

A

A head on overlap of orbitals

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4
Q

Shape and angle around a carbon atom in alkanes

A

Tetrahedral arrangement

Bond angle of 109.5

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5
Q

Rotation around a sigma bond

A

Free rotation

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6
Q

Why can alkanes be separated using fractional distillation?

A

Boiling points of the alkanes are different

BP increases as chain length increases

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7
Q

Why do longer chains have higher boiling points?

A

As chain length increases, surface area increases
There is greater surface contact within the molecule
Greater London forces so more energy is required to overcome these

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8
Q

Effect of branching on boiling point

A

Branched isomers have lower boiling points
More branching - fewer surface points of contact between molecules of the branched alkanes
Fewer London forces
Branching also prevents them packing close together, so there are fewer intermolecular forces

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