Question | Answer |
what are alkANES? | SATURATED hydrocarbons, general formula =
Cn H2n+2 |
How many bonds can carbon atoms form? | 4 (maximum) |
what are cycloalkanes? | ring of carbon atoms general formula= CnH2n |
What are structural isomers? | different arrangements of the same atom |
What structural isomers can alkanes form? | Chain isomers, only when c-c bonds are switched (onto another carbon atom in the chain) is it an isomer. It is the SAME arrangement if it is rotated! |
What do alkanes burn in? | Oxygen |
What happens when alkanes form halogenoalkanes? | FREE RADICAL SUBSTITUTION. |
What is free radical substitution? | Halogens reacting with alkanes, it can only be started by UV LIGHT. |
What are the steps of free radical substitution? | 1)initiation reaction- free radicals produced
2) propagation reactions- free radicals used up- in chain reactions
3)Termination reactions-free radicals form stable molecules |
What is crude oil? | A mixture of hydrocarbons |
What is petroleum? | crude oil, made mostly of alkanes. |
How do you separate crude oil? | Fractional distillation |
What are the steps of fractional distillation? | 1) vaporised at 350c
2)fractionating column- largest dont vaporise turn into residual.
3)vapor goes up- is cooled, and condenses, therefore drawn off.
4) lowest boiling points don't condense- turn into gases |
What happens to the products in fractional distillation? | light fractions are more valuable-higher demand so are stored/sold. Heavy fractions are cracked. |
What is cracking? | Breaking long chained alkanes into smaller hydrocarbons. |
What are the conditions for thermal cracking? | high temp, high pressure. AlkENES are cracked using this method, form POLYMERS. |
What are the conditions for catalytic cracking? | form motor fuels.
aromatic, ZEOLITE catalyst, slight pressure, high temp |
What can alkanes be reformed into? | cycloalkanes and aromatic hydrocarbons |
what are uses of alkane fuels? | methane- used in cooking, central heating
-petrol
-jet fuel
-diesel |
what is the disadvantage of using alkanes? | are expensive, non-renewable, run out, PRODUCE EMISSIONS. |
What emissions are produced from alkanes? | sulfur dioxides- scrubbers used to reduce output. Are poisonous. Produce acid rain- sulfuric acid.
Carbon monoxide- formed by incomplete combustion, is a poisonous gas.
Nitrogen oxide- forms acid rain, causes breathing problems- affects ozone layer. |
What are greenhouse gases? | Formed from alkanes, absorb infrared leading to global warming. |
AlkENES are? | UNSATURATED hydrocarbons. Formula= CnH2n |
Alkene properties? | Are more reactive, have a double bond consisting of a pi and sigma bond. The double bond has a high electron density. |
Adding hydrogen to c=c bonds produces? | AlkANES via ELECTROPHILIC ADDITION |
What are the conditions for electrophilic addition? | nickel catalyst at 150c. |
What happens in electrophilic addition? | Double bond opens- the pi bond is an electron rich area (is nucleophilic), which attracts the electrophile (hydrogen) meaning the hydrogen attaches itself to each of the carbons. |
What is an electrophile? | Are electron pair acceptors, they are short of electrons, therefore are attracted to electron rich areas.
Examples- Positively charged ions- H+
-Polar molecules |
What is an nucleophile (electron rich area)? | A area high in electrons which is attracted to places which don't have enough electrons.
The double bond in C=C is nucleophilic. |
What is a hazard? | anything that can cause harm |
What is a risk? | chance of what you are doing can cause harm |
what is a risk assessment? | is created to reduce risks,
-working in a smaller scale
-appropriate precautions, e.g. wearing eye protection
-safer chemicals- lower concentration
THIS MINIMISES RISK. |
Hydrogen halides form (with a unsymmetrical alkene)? | 2 products, mostly form the most stable carbocation! |
Alkenes do what when they react with halogens and hydrogen halides? | ELECTROPHILIC ADDITION. |
In order of stability, what are the most stable carbocations? | tertiary, secondary, primary. |
What is the two tests for an alkene? | bromine water- turns colourless with alkenes, because the c=c bonds undergo electrophilic addition with bromine water.
Alkenes are oxidised in acidified potassium manganate. turns from purple- to colourless. |
E/z Isomerism? | Double bonds cant rotate, therefore carbons all lie on the same plane (are trigonal planar). Therefore their structural isomers are the same atoms but different arrangement- steroisomerism. |
E isomerism | Is an isomer with DIAGONAL rotation. When the same groups are diagonally across the double bond. |
What is stereoisomerism? | Are atoms with the same structural formula but different arrangement. Because of the lack of rotation, some alkenes have stereoisomers. |
Z isomerism? | Is an isomer with VERTICAL AND HORIZONTAL rotation. When the same groups are vertically or horizontally across the double bond. |
Cis isomerism? | Z isomer. This only applies if they have the same groups attached to them. |
Trans isomerism? | REMEMBER 'trane' is a E isomer. This only applies if they have the same groups attached to them. |
Alkenes can join to form? | additional polymers |
What happens to the double bond in additional polymers? | The double bonds open up to form a long chain- a monomer (a repeated unit) forms lots of polymers! |
What do polymers form? | Plastics (mostly) |
What happens to waste polymer plastics? | waste plastics, can either be buried, recycled, or burned. |
What is the problems with burying plastics? | they are unreactive, and non-biodegradable, meaning they lead to environmental damage. |
What happens in the process of recycling? | plastics are sorted, them melted molded/remodeled down to make new plastics. |
What is the problems of burning plastics? | heat is used, wasting electricity, toxic gases can be released (are prevented using a scrubber to neutralize) |
Properties of biodegradable polymers? | decompose under right conditions.
Are made from starch. Renewable materials- oil fractions. |
What are the problems with biodegradable polymers? | you have to collect and separate them from other plastics. Are more expensive. |