3:2 Alkanes and Halogenoalkanes

Define hydrocarbon

What does saturated mean

Molecule that only contains hydrogen and carbon

No double carbon bonds, all carbons have four bonds and are bonded to H or C.

Another word for crude oil, and what is it a mixture of

How is it separated and what is it separated into

Petroleum is a mixture of hydrocarbons, mostly alkanes.

Separated into fractions by fractional distillation

How does fractional distillation work

1) the crude oil is vaporised at 350 degrees then it goes into a fractionating column and rises up through it. The largest hydrocarbons don’t vaporise at all because there boiling points are too high - they run to the bottom and form a liquid residue.

2) As the crude vapour goes up the fractionating column, it gets cooler. Because the awaken moelcules have different chain lengths, they have diff boiling points to each fraction condenses at a diff temp. These fractions can then be draw off at a diff temp.

3) Hydrocarbons with lowest boiling points don’t condense and are draw off as gases at the top of the column.

Uses for diff length hydrocarbons (going down in hydrocarbon length)

Gases = liquified petroleum gas, camping gas

Petrol

Petrochemicals

Jet fuel, central heating fuel

Diesel fuel

Lubricating oil

Residue = ships, power stations, roofing and road surfacing

What are the two types of cracking, what conditions do they need, what is produced from these and what are the products used for

Thermal cracking:

High temp, high pressure and produces lots of alkenes. These alkenes are used to make polymers such as poly(ethene)

Catalytic cracking:

Uses a zeolite catalyst, slight pressure and high temperature. It produces mostly aromatic hydrocarbons and motor fuels.

Uses a catalyst cuts costs, because the reaction can be done at a low pressure and a lower temp. The catalyst also speeds up the reaction, saving time and therefore money

Why do alkenes make great fuels, and what is the downside of burning alkenes

In what examples do alkenes produce pollutants

Burning just a small amount releases lots of energy, however they release lots of pollutants

Incomplete combustion, producing carbon monoxide or carbon (soot). Complete combustion also produced CO2 which is a greenhouse gas

What is the greenhouse effect

What is global warming

Burning fossil fuels produces greenhouse gases. These gas’s absorb infrared energy and emit some of it back towards earth.

Global warming is the increasing amount of carbon dioxide in out atmosphere that is causing the earth to be warmer via the greenhouse effect.

How are oxides of nitrogen produced?

What can oxides of nitrogen react with?

How are unburnt hydrocarbons and oxides of nitrogen removed?

When high pressure and high temp in a a engine cause nitrogen and oxygen atoms from the air to react together

Hydrocarbons react I sunlight to form group-level ozone (O3) which is a major component of smog → irritates eyes, respiratory problems

Catalytic converts on cars remove unburnt hydrocarbons and oxides of nitrogen from the exhaust.

How sulfur from fossil fuels can cause acid rain, and what are they effects of acid rain

When sulfure is brut it reacts to form sulfur dioxide gas. If it gets into the atmosphere and dissolves in moisture it can make sulfuric acid → causes acid rain

Acid rain destroys trees, vegetation and corrodes buildings

What is a free radical and how do they form

Particle with an unpaired electron, that forms when a covalent bond splits equally, giving one electron to each. The unpaired electron makes them very reactive.

What is a photochemical reaction?

What do chloroflourocarbons contain

One that is started by U.V light.

No Hydrogen

What does ozone do and equation for how ozone’s are formed

What is causing it to break down and what does this look like. Give the overall reaction. In this reaction what is the catalyst

O2 →(u.v) O. + O. Then O2+O.→ O3

Chlorofluorocarbons are breaking it down

CCl3F →(u.v) CCl2F. + .Cl

Cl. + O3 → O2 + ClO.

ClO. + O3 → 2O2 + Cl.

Overall reaction is 2O3 → 3O2 and Cl. Is the catalyst.

What are safer alternatives to CFC’s and why were CFC’s banned?

Hydrofluorocarbons and hydrocarbons . They were banned as the advantages of CFC’s couldn’t outweigh the environmental problems they were causing so they were banned.

What is a nucleophile

Give examples

Electron pair donor

OH-, CN-, NH3 are all nucleophiles

Nucleophilic substitution

Nucleophile attacks a polar molecule. Halogenoalkanes undergo nucleophillic substitutioN

Halogenoalkanes with hydroxides to form alcohols = warm aqueous sodium/potassium hydroxide . Also called hydrolysis as this is what happens with water

Halogenoakanes with cyanide to form nitriles = warm with ethanolic potassium cyanide

Halogenoalkanes with ammonia forms amines = excess ethanolic ammonia. For this reaction just draw one of the H from ammonia donating its electron to N and removing itself.

What makes ammonia continue to react after one nucleophillic substitution reaction?

What is the side product of ammonia with halogenalkane?

Ammonia still has a lone pair of electrons so can react with other Halogenoalkanes or other ammonia giving a mix of products

NH4Br or whatever halogen is displaced

reactivity of Halogenoalkanes

Reactivity of C-F is the the slowest and reactivity of C-I is the fastest. Reactivity is decided by enthalpy (carbon-halogen bod strength).

C-F undergo nucleophilic substitution reactions the slowest and C-I the fastest

Elimination reaction of Halogenoalkanes (alcohols also undergo elimination reactions)

What do the hydroxide ions act as

Warm Halogenoalkane with hydroxide ions dissolved in ethanol and heated under reflux.

OH- acts as a base

Why does CO2 absorb infrared radiation

Equation to remove NO in a catalytic converter

C=O bonds vibrate at infrared radiation. C=O bonds are polar

2NO + CO → N2 + CO2