Paper 2 (7) Flashcards
What are Isomers?
Isomers are molecules that have the same molecular formula, but different structural formulas.
This means they are made of the same atoms, but the atoms are arranged differently.
Organic chemistry is about molecules that contain the element…
Carbon
Each atom of carbon can form ____ strong bonds, with the most common atoms to be bonded to being other ______ atoms or ________ atoms.
Each atom of carbon can form four strong bonds, with the most common atoms to be bonded to being other carbon atoms or hydrogen atoms.
Define Hydrocarbons
Any compound that is formed from carbon and hydrogen only.
Name the first four alkanes in the series
Methane - 1 Carbon atom bonded to 4 Hydrogen
Ethane - 2 Carbon 6 Hydrogens
Propane - 3 Carbon 8 Hydrogen
Butane - 4 Carbon 10 Hydrogen
What is the homologous series?
A homologous series is a group of organic compounds that have similar chemical properties, due to them having the same functional group.
What is the general formula for alkanes?
C(n)H(2n+2)
()=smaller
How many hydrogen atoms are there in an alkane with 5 carbon atoms?
12 hydrogen atoms
An alkane only has s_____ covalent bonds. There are no d_____ bonds or t_____ bonds.
single
double
triple
What is another way to describe hydrocarbons with only single bonds?
Saturated
As the chain length (number of carbon atoms) of alkanes increases, they become:
(viscous/ volatile/ flammable)
More viscous
Less volatile
Less flammable
Increasing the chain length - number of carbons - of alkanes leads to:
(boiling/ melting)
Higher boiling point
Higher melting point
What is the word equation for the complete combustion of a hydrocarbon?
hydrocarbon + oxygen ➔ carbon dioxide + water
C7H16 + ?O2 ➔ ?CO2 + _H2O
The above combustion reaction needs to be balanced. Start by balancing the number of H2O molecules so that the number of hydrogen atoms is equal on both sides of the equation.
8
C7H16 + ?O2 ➔ _CO2 + 8H2O
Next, balance the number of CO2 molecules by making sure there are an equal number of carbons on both sides of the equation.
7
C7H16 + ___O2 ➔ 7CO2 + 8H2O
Finish by balancing the number of O2 molecules, so that there are an equal number of oxygen atoms on both sides of the equation.
11
Is combustion an exothermic or endothermic reaction?
Exothermic
Oxidation is…
Reduction is…
Oxidation is… loss of electrons, gain of oxygen or loss of hydrogen. Reduction is… gain of electrons, loss of oxygen or gain or hydrogen.
During a combustion reaction, are carbon and hydrogen oxidised or reduced?
Carbon (C) becomes CO2, whilst hydrogen (H2) becomes H2O. Both have gained oxygen, so have been oxidised.
How to balance an odd number of oxygens:
Double everything, so the decimal becomes a whole number of molecules
Crude oil is a _______ of many different compounds. Most of the compounds are ____________.
mixture
hydrocarbons
Is crude oil is a finite or renewable resource?
Finite.
We can’t make any new crude oil (at least not quickly), so it is considered a finite resource.
How crude oil was made: 4 steps
1) Crude oil is formed from the remains of dead plants and animals, particularly plankton.
2) These organic remains were covered by mud and sand, and buried in the earth.
3) Over millions of years, these organic remains were compressed under a lot of heat and pressure.
4) The heat and pressure chemically changed the organic remains into crude oil.
Crude oil is a fossil fuel. What else is an example of a fossil fuel?
natural gas
coal
How fractional distillation works with crude oil:
1) Crude oil is a mixture of hydrocarbons with different boiling points.
2) Heat the crude oil to a very high temperature, so that all of the compounds are evaporated from liquid to gas.
3) The hot gaseous hydrocarbons then rise up the fractionating column (because hot gas rises).
4) As they rise, they cool down, because the top of the column is cooler than the bottom.
5) The hydrocarbons will condense when they become cooler than their boiling point, and the liquid hydrocarbons then collect in trays and drain out.
6) The longer chain hydrocarbons condense at the bottom of the fractionating column because they have high boiling points.
7) Meanwhile, the shorter chain hydrocarbons condense at the top of the column because they have much lower boiling points.
Name 2 hydrocarbons which are used as a fuel:
Petrol
Kerosene
Diesel
When separating crude oil we use a fractionating column.
Is the top of the column hotter or cooler than the bottom?
Cooler
What is a feedstock?
A feedstock is a raw material used to provide reactants for an industrial reaction.
What is a petrochemical?
A petrochemical is a substance made from crude oil, via chemical reactions.
The different hydrocarbons in crude oil are all __________, but the useful things we then make from those hydrocarbons (polymers, solvents, lubricants, detergents etc.), are all ______________.
feedstocks
petrochemicals
What can the hydrocarbons in crude oil be used to make?
polymers, solvents, lubricants, detergents
You should also know that the collection of industries and companies that are involved in making petrochemicals are known as the ‘_____________ ________’.
‘petrochemical industry’.
A __________ is a raw material used to provide reactants for an industrial reaction.
feedstock
A __________ is a substance made from crude oil via chemical reactions.
petrochemical
Shorter chain alkanes have _____ melting and boiling points, so are ____ flammable, and ____ volatile.
lower
more
more
Cracking is the process in which ______ chain hydrocarbons are split into _______, more useful hydrocarbons.
Cracking is the process in which larger chain hydrocarbons are split into shorter, more useful hydrocarbons.
What type of reaction is cracking?
It is a thermal decomposition reaction because it involves using heat to break something apart.
What is a redox reaction?
A redox reaction is a reaction in which both oxidation and reduction occur.
What is an acid base reaction?
a chemical reaction that occurs between an acid and a base.
Catalytic cracking: 3 steps
1) First, some long chain alkanes are heated until they vaporise into a gas
2) Then they’re passed over a hot, powdered aluminium oxide catalyst
3) This breaks the long chain alkanes into a shorter chain alkane and an alkene
How is steam cracking different to catalytic cracking?
Steam cracking is different because there is no catalyst involved. Instead, the vaporised long chain alkane is mixed with steam at very high temperatures.
When a long chain alkane is cracked, there aren’t enough ________ atoms to make two alkanes. Hence, cracking will always produce one a_____ and one a_____. (Alkenes are hydrocarbons with a double bond between two carbon atoms).
hydrogen
alkane
alkene
What is an alkene?
Alkenes are hydrocarbons with a double bond between two carbon atoms.
True or false? In cracking, the number of carbon and hydrogen atoms in the reactants and products are always balanced.
True
An unknown alkane was cracked to produce propene (C3H6) and pentane (C5H12).
What is the unknown alkane?
Octane C8H18
Nonane (C9H20) is cracked to produce ethene (C2H4) and one other product.
What is the other product?
Heptane C7H16
1) Alkenes are similar to alkanes. Alkenes are also hydrocarbons and also an example of a ___________ series.
2) The difference is that alkenes have a double bond between two ______ atoms, whereas alkanes only have single bonds.
3) Another way to express the presence of the double bond between two carbon atoms is to say that alkenes are ‘___________’.
homologous
carbon
unsaturated
The double bond in alkenes makes alkenes ________ reactive than alkanes.
more
The test to distinguish between alkanes and alkenes is the _______ water test.
bromine
Bromine test for alkenes
Bromine water (just bromine dissolved in water) by itself is an orange colour.
But, when it’s mixed with alkenes, all of the bromine will react, and so the solution loses its orange colour, and turns colourless.
This doesn’t happen when bromine water is mixed with alkanes, because alkanes are not reactive enough to react with bromine water.
So, when mixed with an alkane, the solution will stay orange.
