F322 Chemistry

Chemistry revision cards for F322 OCR Chemistry

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Basic Concepts

Define empirical formula

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Basic Concepts

The simplest whole number ratio of atoms of each element present in a compound

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Basic Concepts

Define molecular formula

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Basic Concepts

the actual numbr of atoms of each element in a molecule

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Basic Concepts

Define general fomula

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Basic Concepts

The simplest algebraic formula of a member of a homologous series, i.e. for an alkane CnH2n+2

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Basic Concepts

Define Structural Formula

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Basic Concepts

The minimal detail that shows the arrangement of atoms in a molecule e.g. for butane : CH3CH2CH2CH3

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Basic Concepts

Define displayed formula

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Basic Concepts

The relative positionin gof atoms and the bonds between them.

H H

H---C---C---O-H

H H

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Basic Concepts

Define skeletal formula

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Basic Concepts

the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups

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Basic Concepts

What is a homologous series?

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Basic Concepts

A series of organic compounds having the same functional group but with each successive member differing by CH2

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Basic Concepts

What is a functional group?

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Basic Concepts

It is a group of atoms responsible for the characteristic reactions of a compound

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Basic Concepts

What are the names of the first ten members of the alkanes homologous series

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Basic Concepts

Methane

Ethane

Propane

Butane

Pentane

Hexane

Septane

Octane

Nonane and Decane

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Basic Concepts

What is a structural isomer?

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Basic Concepts

compounds with the same molecular formula but different structural formulae

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Basic Concepts

What is a stereoisomer?

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Basic Concepts

compounds with the same structural formula but with a different arrangement in space

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Basic Concepts

What is E/Z isomerism?

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Basic Concepts

It is an example of steroisomerism. When an organic molecule has a carbon-carbon double bond, the bonds are unable to rotate about the double bond. two dfferent groups must be attached to each carbon atom of the C=C for this kind of isomerism to occur.

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Basic Concepts

What is cis/trans isomerism?

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Basic Concepts

It is a special case of E/Z isomerism in which two of the substituent groups are the same. They will either be both above the C=C bond or one above and one below.

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Basic Concepts

Describe the different types of covalent bond fission

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Basic Concepts

There is homolytic bond fission which forms two free radicals when the bond breaks, and an electron goes to each atom

There is heterolytic bond fission which forms a cation and an anion. When the bond breaks, both electrons in the covalent bond go to one atom.

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Basic Concepts

Describe giving an example and equations, the reaction mechanisms of free radical substitution

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Basic Concepts

Initiation : chlorine molecule splits by homolytic fission in the presence of UV light

CL2 --> Cl . + Cl .

Propagation: Free radicals react with other molecules to always produce a free radical

Cl . + CH4 --> CH3 . + HCL

CH3 + CL2 --> CH3CL + CL .

Termination: two free radicals react to end the reaction

CL. + CL. --> CL2

CH3. + CL. --> CH3CL

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Basic Concepts

How do you calculate atom economy?

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Basic Concepts

Molecular mass of the desired products / sum of molecular masses of all products x 100

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Basic Concepts

What atom economy do addition reactions have?

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Basic Concepts

100% atom economy

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Basic Concepts

what type of reaction is less atomically economical than addition reactions?

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Basic Concepts

Substitution reactions

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Basic Concepts

What are the benefits of developing chemical processes with a high atom economy?

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Basic Concepts

You get more for your money and it reduces waste to the environment

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Alkanes

What is a hydrocarbon?

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Alkanes

A compound that contains only hydrogen and carbon

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Alkanes

How is crude oil separated?

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Alkanes

Different fractions of hydrocarbons in crude oil have different boiling points so condense at different temperatures in the fractional distillation column.

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Alkanes

What kind of hydrocarbons are saturated hydrocarbons

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Alkanes

Cycloalkanes and alkanes ( no double bonds)

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Alkanes

what kind of shape is formed around each carbon atom in a hydrocarbon?

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Alkanes

a tetrahedral shape

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Alkanes

Describe and explain the trend in boiling points between long chain alkanes and short chain alkanes

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Alkanes

Long chain alkanes have a higher boiling point as there are more Van der Waals forces in the molecule so requires more energy to overcome

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Alkanes

Describe and explain the trend in boiling points between branched and straight chain alkanes

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Alkanes

Branched chain alkanes have a lower boiling point than straight chain alkanes as there are less contact points for Van der Waals forces so less Van der Waals forces to overcome.

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Alkanes

What is produced from the combustion of alkanes?

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Alkanes

Water and CO2

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Alkanes

What is produced from the incomplete combustion of alkanes. Give an equation

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Alkanes

Carbon monoxide and water

CH4 + 2.5O2 --> CO + 2H2O

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Alkanes

What is catalytic cracking?

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Alkanes

The break down of long chain alkanes to short chain alkanes and alkenes by thermal decomposition using heat and a zeolite catalyst at 450 degrees C

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Alkanes

Why does cracking make more useful fuels?

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Alkanes

Because short chain alkanes have a lower boiling point than long chain alkanes so combust more efficiently. Alkenes are used in the plastics industry

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Alkanes

why are straight chain hydrocarbons changed into branched alkanes and cyclic hydrocarbons?

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Alkanes

Branched chain alkanes and cyclic alkanes are used as additives in fuels to promote efficient combustion

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Alkanes

How are straight chain alkanes changed into cyclic hydrocarbons and arenes and what else is produced?

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Alkanes

Reforming using an ALO3 catalyst and 150 degrees C. Hydrogen is produced which is used in the manufacture of ammonia and margerine

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Alkanes

What the problems associated with fossil fuel use?

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Alkanes

We develop an over-reliance on non-renewable fossil fuel reserves that will one day run out. We need to spend more money on developing renewable plant based fuels I.e biodiesel. Increased CO2 levels from combustion of fossil fuels is leading to global warming and climate change.

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Alkanes

What is a free radical?

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Alkanes

A species with an unpaired electron

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Alkenes

What hydrocarbons are unsaturated hydrocarbons?

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Alkenes

Alkenes and cycloalkenes

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Alkenes

How is a pie bond formed?

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Alkenes

by the overlapping of p orbitals on adjacent carbon atoms with a C=C double bond

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Alkenes

State and explain the shape around each Carbon atom in a C=C double bond

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Alkenes

trigonal planar - 3 areas of electron density - 2 pie bonds and a sigma bond

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Alkenes

How do alkenes react to form alkanes?

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Alkenes

They react with hydrogen in the presence of a nickel catalyst and 150 degrees C in an addition reaction

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Alkenes

How do alkenes react to form dihalogenoalkanes?

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Alkenes

They react with halogens e.g. reacting with bromine to detect a C=C double bond and thus the unsaturation of a molecule.

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Alkenes

How do alkenes react to form halogenoalkanes?

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Alkenes

They react with a hydrogen halide

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Alkenes

How do alkenes react to form alcohols?

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Alkenes

They react with water, H3PO4 catalyst, heat and pressure to form an alcohol

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Alkenes

What is an electrophile?

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Alkenes

An electron pair acceptor

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Alkenes

Describe an electrophilic addition reaction

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Alkenes

There are 2 ( bromine and hydrogenbromide)

HBr

The HBr has a permanent dipole as Br is more electronegative than hydrogen. The delta +ve hydrogen attracts the electrons in the Pie bond of the alkene. The HBr bond splits by heterolytic fission forming a carbocation and Br- ion. Then Br- ion with a lone pair and carbocation react to form a halogenoalkane.

With bromine, the electrons in the pie bond of the alkene repel the electrons in the Br2 bond, inducing a dipole. Then the same thing happens as before.

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Alkenes

What kind of reaction takes place when alkenes polymerise?

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Alkenes

addition polymerisation - the C=C bond opens up

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Alkenes

What is the repeat unit of polypropene?

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Alkenes

CH3 H

------------C----------C-------------

H H

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Alkenes

How are alkenes used in the manufacture of margarine ?

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Alkenes

Alkenes react with H2 gas and a nickle catalyst to produce an alkane and hydrogen which is used to saturate vegetable oils in hydrogenation

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Alkenes

What are the different types of polymer disposal?

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Alkenes

Separation of plastics into types and recycling

- sometimes done by hand, sometimes done by scanning. Types must be labelled

Combustion for energy production

- Burnt to produce heat energy

- Not alot is produced so household waste is added which releases toxic gases

-PVC release HCL so needs alkaline scrubbers to remove gases

Feedstock for cracking

- crack waste into smaller molecules then use as a feedstock to produce plastics

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Alkenes

What are chemists trying to do to minimise harm to the environment with polymer disposal?

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Alkenes

They are trying to remove toxic waste products eg HCL

They are developing biodegradable and compostable polymers i.e. isoprene maize and starch

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Alcohols

Explain the water solubility and relatively low volatility of alcohols

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Alcohols

They hydrogen bonding that occurs with alcohols gives them a very high boiling point and low volatility. Solubility decreases as the chain length increases as a larger part of the alcohol is made up of a non-polar HC chain. The HC chain does not form H bonds with water.

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Alcohols

How is ethanol produced?

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Alcohols

The fermentation of sugar

C6H12O6 ---------------> 2CH3CH2OH + 2CO2

using yeast, no oxygen and 37 degrees C

This is used by the drinks industry and in biofuels

Reacting ethene with steam and H3PO4 catalyst

CH2=CH2 + H2O -----> CH3CH2OH

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Alcohols

How are alcohols used?

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Alcohols

Alcoholic drinks

Sterilizing

Solvents

Biofuels

Fuel dditives

Chemical Feedstocks

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Alcohols

How do you classify alcohols?

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Alcohols

Primary - The -OH group is attached to a C atom with no, or one alkyl group

Secondary - The -OH group is attached to a C atom bonded to two alkyl groups

Tertiary - The -OH group is attached to a C atom bonded to three alkyl groups

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Alcohols

What do alcohols combust to form?

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Alcohols

CO2 and H2O

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Alcohols

What is the oxidising agent that is used for the oxidation of alcohols?

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Alcohols

Acidified potassium dichromate

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Alcohols

What is the colour change in the dichromate?

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Alcohols

Orange ---> green

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Alcohols

What kind of alcohol is oxidised to produce an aldehyde, carboxylic acid and ketone?

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Alcohols

Primary is oxidised to form an aldehyde and then refluxed to form a carboxylic acid

Secondary is oxidised to form a ketone

Tertiary doesn't oxidise

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Alcohol

What is reflux?

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Alcohols

the continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry

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Alcohols

How is an ester produced?

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Alcohols

Alcohol + Carboxylic acid ------> Ester + Water

It uses concentrated Sulfuric acid.

An ester is formed from the removal of a water molecule ( H from the alcohol and OH from the carboxylic acid)

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Alcohols

How is an alkene formed from an alcohol?

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Alcohol

Dehydrating the alcohol using concentrated sulfuric acid and heat

C4H10O ---------> C4H8 + H2O

The removal of water molecules from adjacent C atoms. This is an elimination reaction

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Halogenoalkanes

What kind of reaction is the hydrolysis of halogenoalkanes?

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Halogenoalkanes

nucleophilic substitution

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Halogenoalkanes

Describe a nucleophilic substitution reaction

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Halogenoalkanes

The C--X bond is polar and the hot aqueous NaOH disassociates to form a Na+ ion and OH- ion. The OH- is attracted to the delta positive C atom. The electrons in the C---X bond are repelled by the OH- ion so the bond breaks and forms a C---OH bond and an X- ion and Na + ion.

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Halogenoalkanes

What is a nucleophile?

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Halogenoalkanes

An electron pair donor

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Halogenoalkanes

Explain the rates of hydrolysis of primary halogenoalkanes in terms of relative bond enthalpies of carbon - halogen bonds

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Halogenoalkanes

Down the halogen group, bond enthalpies are less so the C-X bond is weaker making it more reactive as the bond is more easily broken.

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Halogenoalkanes

What is chloroethene and tetrafluoroethene used for?

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Halogenoalkenes

PVC and PTFE ( teflon)

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Halogenoalkanes

Why are halogenoalkanes good aerosols?

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Halogenoalkanes

They have a low boiling point so evaporate at room temperature. They have a low reactivity, volatility and are non toxic

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Halogenoalkanes

How do CFCs cause environmental damage?

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Halogenoalkanes

CFC's don't break down in the lower atmosphere. They are broken down in the stratosphere by UV light to produce free radicals CL . which catalyse the breakdown of O3.

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Halogenoalkanes

What is the role of green chemistry in minimising damage to the environment with regard to CFCs

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Halogenoalkanes

They promote biodegradable alternatives to CFCs such a hydrocarbons and HCFCs, they use CO2 as a blowing agent. They banned the use of CFCs

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Modern Analytical Techniques

What happens to covalent bonds when they absorb infra-red radiation?

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Modern Analytical Techniques

The bonds vibrate

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Modern Analytical Techniques

How do breathalysers work?

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Modern Analytical Techniques

They measure ethanol in the breath by analysis using infra-red spectroscopy

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Modern Analytical Techniques

How can you use Mass Spectrometry to determine the relative isotopic mass or a substance?

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Modern Analytical Techniques

The Mr of the M+ ion is the last peak on the chart

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Modern Analytical Techniques

How is Mass Spectrometry used as a method for identifying elements?

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Modern Analytical Techniques

It is used in the Mars space probe and in monitoring levels of environmental pollution, such as lead.

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Modern Analytical Techniques

What is a mass spectrum essentially?

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Modern Analytical Techniques

It is a fingerprint of the molecule that can be identified by a computer using a spectral database

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Enthalpy Change

What is the enthalpy change for an exothermic and endothermic reaction?

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Enthalpy Change

exothermic - A negative enthalpy change

endothermic - A positive enthalpy change

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Enthalpy Change

What kind of typical reactions are exothermic and endothermic reactions?

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Enthalpy Change

exothermic - oxidation such as the combustion of fuels and the oxidation of carbohydrates such as glucose in respiration. Making brine. All neutralisation reactions

endothermic - Thermal decompositions ( limestone) Photosynthesis and cracking. All of these require the input of heat to start the reaction

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Enthalpy Change

Draw the 2 enthalpy profile diagrams of endothermic and exothermic reactions

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Enthalpy Change

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Enthalpy Change

Define activation energy

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Enthalpy Change

Activation energy is the energy needed to start a reaction. It provides energy to break bonds.

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Enthalpy Change

What are standard conditions and why do we need them?

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Enthalpy Change

Temp 25 degrees c

pressure 1 atmsophere

conc. 1.0 mol/dm3

You can only compare reactions if they conditions are the same

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Enthalpy Change

Define enthalpy change of reaction

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Enthalpy Change

It is the enthalpy change when the molar quantities of reactants shown in the equation for the reaction, react under standard conditions to give the products of their standard states

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Enthalpy Change

Define the enthalpy change of formation

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Enthalpy Change

It is the enthalpy change when one mole of compound in its standard state, is made from its elements in their standard states under standard conditions

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Enthalpy Change

Define enthalpy change of combustion

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Enthalpy Change

It is the enthalpy change when one mole of a substance burns completely in oxygen gas to form products in their standard states under standard conditions

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Enthalpy Change

What is the equation to calculate energy change?

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Enthalpy Change

Q = m x c x delta T

m is the mass of the solvent

c is the specific heat capacity

delta T is the change in temperature

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Enthalpy Change

What makes a reaction endothermic or exothermic?

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Enthalpy Change

A reaction is endothermic when the energy released from forming new bonds is less than the energy required to break the existing bonds.

A reaction is exothermic when the energy released from forming new bonds is more than the energy required to break the existing bonds.

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Enthalpy Change

Define average bond enthalpy

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Enthalpy Change

The energy required to break one mole of a particular type of bond in gaseous molecules under standard conditions. The average of X--Y bond enthalpies measured in different compounds.

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Enthalpy Change

Define Hess's law

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Enthalpy Change

The total enthalpy change for a reaction is the same for any reaction route, provided that the starting and finishing conditions are the same

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Rates and Equilibria

What is the effect of concentration on the rate of reaction?

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Rates and Equilibria

Increasing the concentration increases the rate of reaction because there are more particles in the same volume therefore collisions are more probable and so more frequent. It has no effect on probability of success.

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Rates and Equilibria

What is the affect of an increase in pressure of a gas on the rate of reaction?

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Rates and Equilibria

The higher the pressure, the faster the rate of reaction as the same number of particles are now in a smaller volume so collisions are more probable and so more frequent. It has no effect on the probability of success

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Rates and Equilibria

How is a catalyst useful in a reaction?

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Rates and Equilibria

It speeds up a reaction without being consumed by the overall reaction

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Rate and Equilibria

Explain how catalysts work

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Rates and Equilibria

Catalysts affect the conditions that are needed, often requiring lower temperatures and reducing energy demand and CO2 emissions from burning of fossil fuels.

They enable different reactions to be used with better atom economy and with reduced waste

They are often enzymes, generating very specific products and operating effectively close to room temperatures and pressures

Some have great economic importance e.g. iron in ammonia productions.

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Rates and Equilibria

Explain using enthalpy profile diagrams, how a catalyst speeds up a reaction

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Rates and Equilibria

A catalyst allows a reaction to proceed via a different route with a lower activation energy, giving rise to an increased reaction rate.

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Rates and Equilibria

Explain the Boltzmann distribution and its relationship with activation energy

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Rates and Equilibria

The graph describes the distribution of energy between the particles in a liquid or gas system. The average energy corresponds to T. The Area is the total number of particles in the system. The smaller area indicates the number of particles that have Ea.

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Rates and Equilibria

Describe the effects of temperature on the Boltzmann distribution curve

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Rates and Equilibria

The lower the temperature, the curve shifts to the left and is higher and less molecules have the activation energy. They higher the energy the curve shifts to the right and is lower and more particles have the Ea. The area under the curve must stay the same because the total number of particles in the system does not change.

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Rates and Equilibria

When does a dynamic equilibrium exist?

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Rates and Equilibria

When the rate of the forward reaction is equal to the rate of the reverse reaction

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Rates and Equilibria

State le Chatelier's principle

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Rates and Equilibria

Any change in the conditions of an equilibrium system will result in a shift of the equilibrium position in the direction that opposes that change.

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Rates and Equilibria

Why is important for industry to compromise between chemical equilibrium and rate of reaction?

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Rates and Equilibria

If the temperature needs to be low to have a high yield, the reaction will be too slow so a medium temperature is needed.

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Alkanes

What are the limitations of radical substitution in synthesis?

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Alkanes

products are difficult to predict as the reactions are hard to control as eg for methane and chlorine you could get CH2Cl2 as well as normal products when substitution proceeds further. Therefore atom economy is potentially low.

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Chemistry of the Air

What kind of bonds is infra-red radiation absorbed by?

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Chemistry of the Air

C=O, O-H and C-H bonds in H2O, Co2 and CH4

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Chemistry of the Air

What two factors affect the greenhouse effect of a given gas?

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Chemistry of the Air

The gas's atmospheric concentration and its ability to absorb infra-red radiation

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Chemistry of the Air

Why must we control global warming?

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Chemistry of the Air

Global Warming causes climate change, which threatens habitats and weather systems all over the world.

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Chemistry of the Air

What are the ways in which chemists minimise climate change resulting from global warming?

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Chemistry of the Air

They provide scientific evidence to governments to verify that global warming is taking place

They investigate solutions to environmental problems such as carbon capture and storage.

They monitor progress against initiatives such as the Kyoto protocol

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Chemistry of the Air

What is carbon capture and storage?

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Chemistry of the Air

Capturing CO2 and pumping it into air reserves deep under the sea that used to be used for oil drilling. It is then stored in these large cavities. Injection of CO2 into stable geological structures such as oil and gas fields, unminable coal beds and deep saline formations.

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Chemistry of the Air

How is the ozone sustained?

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Chemistry of the Air

Ozone is continuously being formed and broken down in the stratosphere by the action of ultraviolet radiation.

O2 + O --> O3

O2 + uv light ---> O

O3 + uv light ---> 2O2

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Comments

Alexander Newton

It's a great resource but when i try and print the pages are just blank?

Annabelle

This is brilliant!! Thank you

Maleficent

Waste of paper.

Umair Qaisar

great resource!

Majd Twijiri

GREAT..

Majd Twijiri

what about air pollution and green chemistry?

heloise

Really useful thanks, although I think its "pi" as in the number, not "pie" as in the food :P 

Sanna

That was a brilliant overview thank you :)

Shannon Tennant-Smith - Team GR

Saved this to my favourites; thanks!

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