12.0 Alkanes Flashcards
(20 cards)
Why are alkanes described as saturated
hydrocarbons?
Molecules containing only hydrogen and carbon, bonded by single covalent bonds.
How is crude oil separated into useful products?
Fractional distillation
How does fractional distillation separate crude oil?
Vapourise crude oil.
Enter fractionating column which decreases in
temperature as you go up.
Shorter hydrocarbon molecules have lower boiling points
and travel further up the column before they reach their
boiling point and condense. Similar size molecules
condense at similar temperatures and are collected as a fraction.
Which crude oil fractions tend to be in lower demand?
Longer chain molecules are in greater supply but lower
demand.
What reaction involves breaking carbon-carbon bonds in alkanes?
Cracking
What are the two types of cracking and the conditions needed?
Thermal – high temperature and pressure
Catalytic – zeolite catalyst, slight pressure and high
temperature
What types of products are mainly produced from
thermal and catalytic cracking?
Thermal – alkenes
Catalytic – motor fuels and aromatic compounds
What is cracking economically important?
Changes less useful, longer chain alkanes into shorter, more useful molecules with greater demand (such as alkenes and motor fuels)
What are the two types of combustion?
Complete and incomplete
What are the two reactants in all types of
combustion?
Fuel (or give example) and oxygen
What are the two products of complete combustion
of alkanes?
Carbon dioxide and water
What are the three possible products of incomplete
combustion of alkanes?
Water, carbon monoxide, carbon
Explain how is NOx formed during combustion in an
engine?
Nitrogen and oxygen (from air)
React under high temperatures and pressures
Why is SO2 formed during combustion of
hydrocarbons?
Sulfur impurities in fuel
React with oxygen from the air
What is flue gas desulfurisation?
Use of CaO or CaCO3 to neutralise SO2 vapours before they enter the atmosphere.
Write a balanced equation to show the reaction in a
catalytic converter.
2CO + 2NO → N2 + 2 CO2
What substance(s) are used as the catalyst in a
catalytic converter?
Pt/Pd/Rh
What conditions are required for chlorination of
alkanes?
UV light
List the main steps in chlorination of alkanes.
Initiation
Propagation
Termination
Write balanced equations to show all key steps in
chlorination of methane to form chloromethane.
I: Cl2 → 2 Cl∙
P1: Cl∙ + CH4 → CH3∙ + HCl
P2: CH3∙ + Cl2 → CH3Cl + Cl∙
T1: CH3∙ + Cl∙ → CH3Cl
(T2: 2 CH3∙ → CH3CH3)
(T3: 2 Cl∙ → Cl2)
