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