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OCR Chemistry - Exams > Module 4 - Core Organic Chemistry - Exam Questions > Flashcards

Module 4 - Core Organic Chemistry - Exam Questions Flashcards

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1
Q

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)

A

Has OH bonds

Forms hydrogen bonds with water molecules

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2
Q

What type of stereoisomerism is shown by alkenes? (1)

A

E/Z isomerism

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3
Q

Identify the two main methods used in the industrial production of ethanol.
Write an equation for each method (4)

A

Fermentation of sugars
C6H12O6 -> 2C2H5OH + 2CO2
Hydration of ethene
C2H4 + H2O -> C2H5OH

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4
Q

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)

A

Ester

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5
Q

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)

A

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

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6
Q

Write a balanced equation for the oxidation of ethanol to ethanoic acid. Use [O] to
represent the oxidising agent (2)

A

C2H5OH + 2[O] -> CH3COOH + H2O

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7
Q

Fermentation only occurs in the presence of yeast. State two other essential
conditions (2)

A

Choose 2 from:
Warm to just above room temp
Aqueous
Anaerobic

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8
Q

How would you know when fermentation of glucose is complete? (1)

A

No more bubbles

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9
Q

State a suitable reagent for dehydrating an alcohol (1)

A

H3PO4

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10
Q

Explain what is meant by low volatility (1)

A

High boiling point

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11
Q

Explain what is meant by intermolecular bonds (1)

A

Bonds between molecules

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12
Q

What type of intermolecular bond is found between alcohol molecules? (1)

A

Hydrogen bonds

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13
Q

State a suitable oxidising mixture for an alcohol to a carboxylic acid (1)

A

H2SO4/K2Cr2O7

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14
Q

State a suitable catalyst for esterification (1)

A

H2SO4

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15
Q

Citronellol has a C=C, state what you would see when bromine is added (1)

A

Decolourises

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16
Q

Suggest a catalyst for hydrogenation (1)

A

Nickel

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17
Q

Kerosene is obtained from crude oil. Name the process used to obtain kerosene from crude oil and explain why the process works (2)

A

Fractional distillation

Because fractions have different boiling points

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18
Q

Explain why the straight chain isomer of C10H22 has a higher boiling point than
any of its branched chain structural isomers (2)

A

Decane has more surface contact

Decane has more London forces

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19
Q

Explain why the straight chain isomer of C10H22 is converted by the petroleum
industry into its branched chain isomers (1)

A

Branched chains have more efficient combustion

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20
Q

Suggest, with the aid of an equation, how NO is formed within an aeroplane
engine (1)

A

N2 + O2 -> 2NO

21
Q

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)

A 
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
22
Q

What is the name of the process used to convert long chain alkanes into more useful shorter chain alkenes? (1)

A

Cracking

23
Q

Why does incomplete combustion sometimes take place? (1)

A

Not enough O2

24
Q

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)

A

Cl• + O3 -> •ClO + O2
•ClO + O -> Cl• + O2
Overall: O3 + O -> 2O2

25
Q

As number of carbon atoms in the alkyl chain increases, boiling point increases. Explain this trend (1)

A

More intermolecular forces

26
Q

What is meant by the term radical? (1)

A

Species with an unpaired electron

27
Q

State the conditions necessary to bring about the formation of the chlorine free radicals from Cl2 (1)

A

UV light

28
Q

State the type of bond fission involved in the formation of the chlorine radicals (1)

A

Homolytic fission

29
Q

State what is meant by the term hydrocarbon (1)

A

Compound containing hydrogen and carbon only

30
Q

Suggest a type of reactant that could be used to remove the HCl after it is formed from a polymer’s incineration (1)

A

Alkali

31
Q

Disposal of polymers causes environmental damage

Describe two ways chemists can reduce this damage (2)

A

Develop photodegradable polymers

Develop biodegradabale polymers

32
Q

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)

A

Separation into types and recycling

Combustion for energy generation

33
Q

What is meant by the term

electrophile? (1)

A

Electron pair acceptor

34
Q

State the problem associated with the combustion of polymers such as pvc (1)

A

Harmful fumes are produced

35
Q

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)

A

Crack polymers

Used a feedstock

36
Q

State the type of polymerisation that alkenes undergo (1)

A

Addition polymerisation

37
Q

What is meant by unsaturated? (1)

A

Contains a double bond

38
Q

Explain the term atom economy (1)

A

Sum of the molecular masses of the desired products/sum of molecular masses of all products
As a percentage

39
Q

A compound has a double bond but does not have E/Z isomerism, why? (1)

A

One of the C in C=C is joined to two groups that are the same

40
Q

CFCs are now largely banned because of their ozone-depleting properties
Suggest two reasons why there is still concern about ozone depletion (2)

A

CFCs are still being used

There are other ozone depleting substances

41
Q

Suggest which bond is most likely to be broken when CF3Cl is exposed to
ultraviolet radiation. Explain your answer (1)

A

C-Cl bond

Weaker bond

42
Q

Explain what is meant by the term homolytic fission (2)

A

Homolytic - bonded pair split equally

Fission - bond breaking

43
Q

Explain why 1-iodopropane is hydrolysed faster than 1-bromopropane (2)

A

C-I bonds broken more easily

C-I bonds have less bond enthalpy

44
Q

State a use of mass spectrometry outside of the laboratory (1)

A

Breathalysers

45
Q

An alcohol is oxidised to an aldehyde, why is the reaction carried out with distillation not under reflux (2)

A

Distillation allows loss of volatile components

Prevents formation of RCOOH

46
Q

Suggest how an HBr molecule can act as an electrophile (1)

A

H atom of HBr accepts a pair of electrons

47
Q

Explain how you would obtain a dry, pure sample of organic product, starting from the two layers? (4)

A

-Add layers to a separating funnel;
-Run off each layer (organic & aqueous) through the tap AND collect top
layer;
-Add an anhydrous salt to dry organic layer (e.g.
MgSO4, CaCl2);
-Redistill AND collect fraction distilling at 116 ºC;

48
Q

Draw a labelled diagram to show how you would safely set up apparatus for distillation and describe
a method to obtain a pure sample of cyclohexanone from the distillate? (6)

A 
Includes following components:
-distillation flask
-heat source
-thermometer at outlet (bulb level with outlet)
-still-head
-water condenser (correct direction of water
flow)
-receiving vessel
-open system.

Further purification
-Shake and leave to settle in a separating
funnel;
-Separate layers by tapping off;
-Add (a small amount of) anhydrous
magnesium sulfate/anhydrous calcium chloride
to organic layer (in a dry conical flask);
-(Re)distil the organic layer;
-Collect fraction distilling at (between 150 °C
and) 156 °C.

OCR Chemistry - Exams (7 decks)

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