Alkanes Flashcards

1
Q

What is the general formula for alkanes

A

CnH2n+2

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2
Q

Are alkanes saturated or unsaturated

A

Saturated as they only contain single bonds

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3
Q

What is the general formula for cycloalkanes

A

Cnh2n

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4
Q

How to carry out fractional distillation

A

Crude oil is vaporised at 350 degrees
Goes through a fractionating column and as it goes up it gets cooler.
Due to the alkane molecules different chain lengths, they have different boiling points so each fraction condenses at a different temperature
Hydrocarbons with the lowest boiling point do not condense, they’re drawn off as gases at the bottom

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5
Q

Why are fractions cracked

A

To make them into more useful smaller molecules

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6
Q

What is cracking

A

Breaking long chained alkanes into smaller hydrocarbons by breaking the c-c bonds

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7
Q

Describe thermal cracking

A

High temp up to 1000 degrees, High pressure up to 70 atm
Produces alkenes which are used to make valuable products like polymers

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8
Q

Describe catalytic cracking

A

Uses Zeolite catalyst at slight pressure and high temp around 450 degrees
Produces aromatic hydrocarbons and motor fuels
Catalysts cut costs by using slight pressure and saves time

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9
Q

What are the products of combustion

A

Water and carbon dioxide

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10
Q

What is incomplete combustion

A

When there is not enough oxygen so the products are carbon monoxide and water
Can also form carbon soot which can cause breathing problems

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11
Q

What happens when engines dont burn all of the fuel molecules

A

They make unburnt hydrocarbons

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12
Q

How are oxides of nitrogen produces

A

High pressure and temp of a car engine causes the particles from the air to react together

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13
Q

When to hydrocarbons and nitrogen oxides react

A

In the prescence of sunlight to form ground level ozone which is a component of smog

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14
Q

What forms when Sulphur is burnt

A

Sulfur dioxide gas

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15
Q

How is sulfur dioxide gas converted into acids rain

A

In the atmosphere it dissolve in the moisture and gets converted into sulphuric acid and then acid rain

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16
Q

What does acid rain do

A

Destroys trees
Kills fish
Corrode buildings

17
Q

How can sulfur dioxide be removed from power station fuel gases before it gets into the atmosphere

A

Powdered calcium carbonate/calcium oxide is mixed with water to make an alakaline slurry. When this slurry mixes with the flue gases the acidic sulfur dioxide gas reacts with the calcium compounds to form a harmless salt - Calcium sulphite

18
Q

What is a free radical

A

A particle with an unpaired electron
The unpaired electron makes them very reactive

19
Q

What is needed fora free radical reaction

A

UV light

20
Q

How do free radicals form

A

A covalent bond splits equals giving one electron to each atom