organic chemistry (p2) Flashcards
What is crude oil?
a mixture of a large number of compounds, most of which are hydrocarbon
How was crude oil formed?
from the remains of organisms that lived and died millions of years ago (mainly plankton which was buried in the mud)
Is crude oil a finite or renewable resource?
Finite
What is a hydrocarbon?
a compound made up of carbon and hydrogen only
Why type of bond joins the carbon and hydrogen atoms in a hydrocarbon
covalent bond
What is an organic compound?
compounds containing carbon atoms covalently bonded to other atoms
What is a homologous series?
a family of organic compounds with the same general formula and similar properities
What is the general formula for alkanes?
CโHโโโโ
What are the names of the first four members of the alkanes?
Methane
Ethane
Propane
Butane
What do the names of alkanes always end in?
-ane
How many bonds does carbon form in a compound?
four
How many bonds does hydrogen form in a compound?
1
How are the different compounds in crude oil separated?
Fractional distillation
What is a fraction?
a mixture of hydrocarbons with a similar number of carbon atoms
What are the products of fractional distillation used for?
- fuels
- starting materials for the petrochemical industry
What are the names of some fractions produced in fractional disillation?
- petrol
- diesel oil
- kerosene
- heavy fuel oil
- liquefied petroleum gases
What useful materials are produced by the petrochemical industry?
- solvents
- lubricants
- polymers
- detergents
How does the temperature of the fractionating column change as you move from bottom to top?
the temperature decreases
What happens when crude oil is heated before entering the fractionating column?
the crude oil evaporates
What happens to the crude oil vapours as they travel up the fractionating column?
- they cool and condense
- when they condense they are collected
Describe how crude oil is seperated in fractional distillation
- Crude oil is heated and it evaporates
- The crude oil vapours enter the fractionating column and travel upwards
- The temperature of the fractionating column decreases towards the top
- As the vapours travel up they cool and condense at different temperatures depending on their boiling points
Where are the long chain hydrocarbons collected in fractional distillation?
At the bottom of the fractionating column
Where are the short chain hydrocarbons collected in fractional distillation?
At the top of the fractionating column
What causes the hydrocarbons to sepeate in fractional distillation?
They have different boiling points and so condense at different levels
When will the hydrocarbons condense in the fractionating column?
When the temperature drops below their boiling point
Why do short chain hydrocarbons collect at the top of the fractionating column?
They have low boiling points and so condense at lower temperatures
Why do large chain hydrocarbons collect at the bottom of the fractionating column?
They have large boiling points and so condense at higher temperatures
If a hydrocarbon boils at 300 แตC, what temperature will it condense at?
300 แตC
What bonds break when hydrocarbons melt and boil?
Intermolecular forces
What type of force holds hydrocarbon molecules together?
Intermolecular forces
What does viscosity it mean?
How much a fluid resists flow (how gloopy it is)
What does volatility mean?
How easy it is to turn a substance into a gas
What does flammability mean?
How easy it is to ignite a substance
As hydrocarbon molecules get bigger, what happens to their viscosity?
increases
As hydrocarbon molecules get bigger, what happens to the boiling point?
increases
As hydrocarbon molecules get bigger, what happens to their flammability?
decreases
Why does the viscosity of hydrocarbons increase as the hydrocarbon molecules get bigger?
As the hydrocarbon molecules get bigger, the intermolecular forces get stronger and move over each other less easily
Why does the boiling point of hydrocarbons increase as the hydrocarbon molecules get bigger?
As the hydrocarbon molecules get bigger, the intermolecular forces get stronger and require more energy to break
Which are better fuels - long or short chain hydrocarbons?
Short chain (they are more flammable)
What is combustion?
reaction with oxygen (burning)
What is complete combustion?
burning in a plentiful supply of oxygen
What are the reactants in complete combustion of a hydrocarbon?
hydrocarbon + oxygen
What are the products in complete combustion of a hydrocarbon?
carbon dioxide + water
What is cracking?
the breaking of longer chain hydrocarbons into shorter, more useful hydrocarbons
Why do we โcrackโ hydrocarbons?
to produce smaller, more useful molecules
What is the reactant in cracking?
longer chain alkanes
Why is cracking a thermal decomposition reaction?
the longer chain hydrocarbons breakdown when heated
What are the products in cracking?
a shorter chain alk๐ฎ๐ป๐ฒ and a short chain alk๐ฒ๐ป๐ฒ
What is thermal decomposition?
the breakdown of a substance when it is heated
Name two types of cracking
- steam
- catalytic cracking
Describe the process of steam cracking
- Long chain hydrocarbons are heated and they evaporate
- The hydrocarbon vapour is heated to a very high temperature and mixed with steam
- The hydrocarbons are broken into smaller hydrocarbons
Describe the process of catalytic cracking
- Long chain hydrocarbons are heated and they evaporate
- The hydrocarbon vapour is then passed over a catalyst
- The hydrocarbons are broken into smaller hydrocarbons
[๐๐ถ๐ด๐ต๐ฒ๐ฟ ๐๐ถ๐ฒ๐ฟ] What is the general formula for alkenes?
CโHโโ
Which are more reactive: alkanes or alkenes?
Alkenes
What is used to test for alkenes?
bromine water
What colour is bromine water?
orange
What colour does bromine water turn when added to alkenes?
colourless
What colour does bromine water turn when added to alkanes?
stays orange
What are alkenes used for?
to make polymers and as the starting material when making many other chemicals
