C6.2 Flashcards
What are hydrocarbons
Hydrocarbons are compounds containing only hydrogen and carbon atoms.
Why do alkanes form a homologous series
They form a homologous series as they have features in common
What are the carbon atoms joined to each other by and are alkanes saturated or unsaturated
They are joined together by single covalent bonds, they are saturated.
What do alkanes burn in and what do they produce
The burn in oxygen in air, carbon atoms are oxidised to carbon dioxide and hydrogen atoms oxidised to water.
When does incomplete combustion occur
Incomplete combustion occurs when there is a poor supply of oxygen.
What are the products of incomplete combustion
Carbon monoxide, water and carbon are produced.
What is the homologous feature of an alkene
They have one double bond
What is the general formula for alkenes
CnH2n
What is the general formula for alkanes
CnH2n+2
When there is one carbon what is the prefix
Meth
When there is two carbons what is the prefix
Eth
When there is three carbon what is the prefix
Prop
When there is four carbon what is the prefix
But
When there is five carbon what is the prefix
Pent
When there is six carbon what is the prefix
Hex
What is a functional group
A functional group is an atom, group of atoms or type of bond in a molecule responsible for the characteristic reactions of the substance.
What is the functional group of alkenes
C=C
What is the test for an alkene or alkane
Add bromine water, if it’s an alkene the solution turns colourless as bromine reacts with alkenes but not alkanes.
When do alkenes undergo addition reactions with hydrogen
When there is a nickel catalyst present.
What is the functional group of an alcohol
-OH (hydroxyl) group
What is the general formula for an alcohol
CnH2n+1(OH)
What can alcohols undergo
Complete and incomplete combustion with the same products as before
What is the functional group for carboxylic acids
-COOH
General formula for carboxylic acids
CnH2n+1COOH
Draw ethanoic acid
How are carboxylic acids formed
They are formed when alcohols react with oxidising agents such as potassium manganate solution.
What reactions can carboxylic acids take part in
.Metals to produce salts and hydrogen
.Alkalis and bases to produce salts and water
.Carbonates to produce salts, water and CO2
What is the colour change when potassium manganate reacts with ethanol
The colour changes from purple and are reduced to pink.
What is crude oil
Crude oil is a fossil fuel. It was formed from the remains of marine organisms that lived many years ago. They were buried deep in the sea bed after they died. Chemical reactions turned them into crude oil.
What two types of resources is crude oil
It is a finite resource and is also a non-renewable resource
How are the different alkanes in crude oil seperated
Using fractional distillation
Why does fractional distillation work
This works because the alkanes have different boiling points
What do larger alkanes have
The larger the molecules the stronger the intermolecular forces and the higher the boiling point.
What is the process of fractional distillation
Crude oil is heated and the vapours are pipe into the bottom of a fractionating column. This has a temperature gradient - hotter at the bottom than the top. They then condense into a liquid where it’s cool enough. The separated parts of crude oil are called fractions. Each fraction contains substances with similar melting points.
What is cracking
A chemical reaction that converts large alkane molecules into smaller alkane and alkene molecules
What is the process of cracking
Heating oil fractions to a high temperature and passing it over a hot catalyst of alumina or silica. The covalent bonds between the large alkane molecules break.
What are the characteristics of large alkanes
They have high boiling points are viscous and are difficult to ignite.
Why is cracking used
Fractional distillation produces more of the larger molecule fractions and less small molecule fractions.
What are polymers made up of
They are made up of smaller monomers joined together.
What are the conditions needed for addition polymerisation
A high temperature and catalyst
What can all alkenes be used for
Addition polymerisation
Draw poly ethene
What are the monomers in DNA
The nucleotides
What are the nucleotides made of
A sugar (deoxyribose), a phosphate, an organic base (A,C,T,G)
What are the four different bases for DNA
Adenine
Guanine
Cytosine
Thymine
What do the nucleotides join end to end to form
One long strand of DNA
What do the two strands of DNA do
They spiral around each other in opposite directions. Hydrogen bonds then form between the bases. This forms DNA.
What are proteins made from
Proteins are made from amino acids (monomers)
What do amino acids have at the end of them
Each amino acid has a functional group at the end so they can join each other end to end.
What are carbohydrates compounds of
They are compounds of carbon, hydrogen and oxygen. They include sugars such as sucrose and complex carbohydrates such as starch.
What happens in condensation reactions
In a condensation reaction two larger molecules react together to form one larger molecule and one smaller molecule.
What happens when carboxylic acids react with alcohols
They form esters as the -COOH react with -OH to produce water and the ester group -COO- which links together the rest of the carboxylic acid and alcohol.
What are condensation polymers
Condensation polymers are polymers formed from condensation reactions.
What does a monomer need to have for this to occur
It needs to have a functional group at both ends of the monomer.
What are polyesters made from
They are made form dicarboxyls and dialcohols. They are polyesters as they contain the functional group -COO.
What are polyamids made from
They are made from a dicarboxyl and a diamine. This produces polyamids with the functional group -CONH-
Difference between addition polymerisation and condensation polymerisation
Happens with a catalyst at high temperatures and pressure. However condensation polymerisation can happen without a catalyst at room temperature and pressure.
What happens in a battery
Exothermic reactions in the cell develop a potential difference between two ends When it’s connected to an electrical circuit a current flows through the cell.
When does a P.D stop being produce
It produces electricity until the reactants are used up.
How does a fuel cell produce electricity
It produces electricity through a chemical reaction between a fuel and oxygen, without combustion occuring.
What is the reaction between hydrogen and oxygen
It’s an exothermic reaction that produces water vapour.
What happens at the anode of a fuel cell
Oxidation occurs and hydrogen loses electrons.
2H2 (G) -> 4H+ (aq) + 4e-
What happens to the hydrogen ions after this
They pass through a proton exchange membrane to the other side of the fuel cell, the electrons travel through the external circuit to the other side of the fuel cell.
What happens at the other side of the fuel cell
Hydrogen ions combine with oxygen and electrons at the other side to form water vapour. 4H+ + O2 + 4e- -> 2H2O
What happens at the cathode of the fuel cell
At the cathode reduction occurs.
