Module 4 - Core Organic Chemistry - Exam Questions Flashcards
Ethane-1,2-diol can be dissolved in water to act as an anti-freeze in car radiators. Explain why ethane-1,2-diol is very soluble in water (2)
Has OH bonds
Forms hydrogen bonds with water molecules
What type of stereoisomerism is shown by alkenes? (1)
E/Z isomerism
Identify the two main methods used in the industrial production of ethanol.
Write an equation for each method (4)
Fermentation of sugars
C6H12O6 -> 2C2H5OH + 2CO2
Hydration of ethene
C2H4 + H2O -> C2H5OH
A student heated an alcohol with a carboxylic acid in the presence of an acid catalyst. Name the functional group of the organic product (1)
Ester
Ethanol can be manufactured by fermentation of sugars (C6H12O6 -> 2C2H5OH + 2CO2) or hydration of ethene (C2H4 + H2O -> C2H5OH)
Compare the sustainability of these methods in terms of: availability of starting materials and energy requirements, and atom economy (7)
Availability of materials:
Sugar is renewable because it can be grown
Ethane is finite because it is from processing crude oil
Energy:
Fermentation - energy required for distillation
Hydration - energy required to generate steam
Atom economy:
AE fermentation < AE hydration
For hydration, ethanol is the only product
AE fermentation could be increased by finding a use for CO2
Write a balanced equation for the oxidation of ethanol to ethanoic acid. Use [O] to
represent the oxidising agent (2)
C2H5OH + 2[O] -> CH3COOH + H2O
Fermentation only occurs in the presence of yeast. State two other essential
conditions (2)
Choose 2 from:
Warm to just above room temp
Aqueous
Anaerobic
How would you know when fermentation of glucose is complete? (1)
No more bubbles
State a suitable reagent for dehydrating an alcohol (1)
H3PO4
Explain what is meant by low volatility (1)
High boiling point
Explain what is meant by intermolecular bonds (1)
Bonds between molecules
What type of intermolecular bond is found between alcohol molecules? (1)
Hydrogen bonds
State a suitable oxidising mixture for an alcohol to a carboxylic acid (1)
H2SO4/K2Cr2O7
State a suitable catalyst for esterification (1)
H2SO4
Citronellol has a C=C, state what you would see when bromine is added (1)
Decolourises
Suggest a catalyst for hydrogenation (1)
Nickel
Kerosene is obtained from crude oil. Name the process used to obtain kerosene from crude oil and explain why the process works (2)
Fractional distillation
Because fractions have different boiling points
Explain why the straight chain isomer of C10H22 has a higher boiling point than
any of its branched chain structural isomers (2)
Decane has more surface contact
Decane has more London forces
Explain why the straight chain isomer of C10H22 is converted by the petroleum
industry into its branched chain isomers (1)
Branched chains have more efficient combustion
Suggest, with the aid of an equation, how NO is formed within an aeroplane
engine (1)
N2 + O2 -> 2NO
Describe the mechanism for the radical substitution of methane by bromine to
make bromomethane
Use the mechanism to suggest why a small amount of ethane is also formed (7)
Initiation: Br2 -> 2Br• Propagation: Br• + CH4 -> HBr + •CH3 •CH3 + Br2 -> CH3Br + Br• Termination: Br• + •CH3 -> CH3Br Ethane made when two methyl radicals react •CH3 + •CH3 -> C2H6
What is the name of the process used to convert long chain alkanes into more useful shorter chain alkenes? (1)
Cracking
Why does incomplete combustion sometimes take place? (1)
Not enough O2
Chlorine radicals, Cl•, catalyse some reactions
Write down an equation for the overall reaction and show how they are not consumed by the overall reaction (3)
Cl• + O3 -> •ClO + O2
•ClO + O -> Cl• + O2
Overall: O3 + O -> 2O2
As number of carbon atoms in the alkyl chain increases, boiling point increases. Explain this trend (1)
More intermolecular forces
What is meant by the term radical? (1)
Species with an unpaired electron
State the conditions necessary to bring about the formation of the chlorine free radicals from Cl2 (1)
UV light
State the type of bond fission involved in the formation of the chlorine radicals (1)
Homolytic fission
State what is meant by the term hydrocarbon (1)
Compound containing hydrogen and carbon only
Suggest a type of reactant that could be used to remove the HCl after it is formed from a polymer’s incineration (1)
Alkali
Disposal of polymers causes environmental damage
Describe two ways chemists can reduce this damage (2)
Develop photodegradable polymers
Develop biodegradabale polymers
Once polymers have been used, they become waste.
Outline two ways that waste polymers are processed usefully, rather than just dumped in landfill sites. (2)
Separation into types and recycling
Combustion for energy generation
What is meant by the term
electrophile? (1)
Electron pair acceptor
State the problem associated with the combustion of polymers such as pvc (1)
Harmful fumes are produced
State two ways in which chemists are trying to minimise the damage to the environment caused by the disposal of halogenated plastics such as pvc (2)
Crack polymers
Used a feedstock
State the type of polymerisation that alkenes undergo (1)
Addition polymerisation
What is meant by unsaturated? (1)
Contains a double bond
Explain the term atom economy (1)
Sum of the molecular masses of the desired products/sum of molecular masses of all products
As a percentage
A compound has a double bond but does not have E/Z isomerism, why? (1)
One of the C in C=C is joined to two groups that are the same
CFCs are now largely banned because of their ozone-depleting properties
Suggest two reasons why there is still concern about ozone depletion (2)
CFCs are still being used
There are other ozone depleting substances
Suggest which bond is most likely to be broken when CF3Cl is exposed to
ultraviolet radiation. Explain your answer (1)
C-Cl bond
Weaker bond
Explain what is meant by the term homolytic fission (2)
Homolytic - bonded pair split equally
Fission - bond breaking
Explain why 1-iodopropane is hydrolysed faster than 1-bromopropane (2)
C-I bonds broken more easily
C-I bonds have less bond enthalpy
State a use of mass spectrometry outside of the laboratory (1)
Breathalysers
An alcohol is oxidised to an aldehyde, why is the reaction carried out with distillation not under reflux (2)
Distillation allows loss of volatile components
Prevents formation of RCOOH ( carboxylic acids )
Suggest how an HBr molecule can act as an electrophile (1)
H atom of HBr accepts a pair of electrons
