topic 7 Flashcards
What is crude oil?
A mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
What is a hydrocarbon?
A compound made up exclusively of hydrogen and carbon atoms
What are alkanes?
Saturated hydrocarbons of a general formula CnH2n+2
What is a homologous series?
Series of compounds with same general formula, same functional groups and similar chemical properties
Describe the combustion of hydrocarbons
- Exothermic reaction occurring when hydrocarbons are reacted with oxygen.
- Complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised)
- Incomplete combustion produces carbon or carbon monoxide and water
Describe the physical properties of alkanes
- First few in series are gases, then change to liquids, then to solids
- Generally, boiling points and viscosity increase as molecules get bigger
- Volatility and flammability decrease as molecules get bigger
- Poor reactivity
Explain how fractional distillation of crude oil takes place
- Crude oil is heated and vaporised
- Vapor rises up in the fractioning column (tower)
- The column is hotter at the bottom and cooler at the top
- Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
- Large molecules, high boiling points – collected at the bottom
- Small molecules, low boiling points – collected at the top
- This gives fractions, which can be used in various ways
What is cracking?
When large hydrocarbons are thermally broken down into smaller and useful molecules
What type of reaction is cracking?
Thermal decomposition
What are the conditions for cracking?
Reactant heated to vapor, passed over a hot catalyst (catalytic cracking) or heated to vapor, mixed with steam and heated to high temperatures (steam cracking)
How are products of cracking used?
The products are alkanes and alkenes – used as polymers and starting materials for synthesis
What is an alkene?
Unsaturated hydrocarbon. Contains a C=C bond.
General formula for alkenes is: CnH2n
What is the test for alkenes?
Add bromine water. Colour change occurs from orange to colourless
Describe the combustion of alkenes
They burn with smoky flames due to incomplete combustion
Describe addition reactions of alkenes
Addition atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond
- With hydrogen – hydrogenation; requires a higher temperature and a nickel catalyst
- With steam – hydration; requires high temperature, pressure and concentrated phosphoric acid (H3PO4) as a catalyst
- With Br2/Cl2/I2 – addition of halogens
What is an alcohol?
An organic compound that contains an -OH functional group
State characteristics of methanol, ethanol, propanol and butanol
- Dissolve in water to form a neutral solution
- React with sodium to form hydrogen
- Burn in oxygen
- React with carboxylic acids in presence of acid catalyst to form esters
Oxidation of the alcohols leads to..?
Carboxylic acids!
Name 3 uses of alcohols:
Fuels, solvents, drinks, disinfectant
State the conditions required for fermentation of glucose and state the equation of the reaction
30-37 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added
C6h12O62CH3CH2OH + 2CO2
What are carboxylic acids?
Organic compounds that contain a COOH functional group
State characteristics of carboxylic acids
- Dissolve in water to form an acidic solution (contains H+ ions)
- React with metal carbonate to form carbon dioxide
- React with alcohols with an acid catalyst to produce esters
- React with metals to give off hydrogen gas
What type of acid is carboxylic acid?
it is a WEAK acid
Explain why carboxylic acids are weak acids
They are partially dissociated in water, thus the pH of a carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration
What is an ester and how is it formed?
An organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst
They have a fruity smell
What is a polymer?
A polymer is a long chain molecule which is made by lots of smaller molecules (monomers) joining together
How do molecules containing a C=C bond form polymers?
C=C bonds open up and many smaller molecules (monomers) join together to from a chain (a polymer) – no other products are made
This is called an “addition polymerisation” reaction
Give 3 examples of addition polymers and their uses
Polyethene- plastic bags
(poly) tetrafluoroethene (PTFE) – Teflon surfaces, for use in non-stick kitchenware
(poly) chloroethene (polyvinylchloride, PVC) – water pipes
What is a repeating unit of a polymer?
It is a smallest structure which, upon numerous translations, yields the structure of the polymer
Drawn by taking monomer and changing C=C to C-C and additional single bonds extending away from these carbons past the brackets
What is a condensation polymer?
It is a polymer made in condensation polymerisation
In this reaction, many molecules (monomers) join together; the polymer is formed but also a small molecules is released e.g. H2O or HCl
Polyesters e.g. terylene
Polyamides e.g. nylon
What is an amide bond?
An amide bond is similar to the ester bond, with O replaced by N e.g. (C=O)-NH2
Just like an ester, it contains the C=O group
What is an amino acid?
It is an organic compound that contains both a carboxylic acid functionality (COOH) and an amine functional group (-NH2)
How do amino acids make proteins? What are polypeptides?
By numerous condensation polymerisation reactions; proteins are polymers made of amino acids (monomers)
*polypeptides are also made by condensation polymerisation of amino acids, but are shorter than proteins (or not folded to form final product). Proteins can be thought of as many polypeptide chains bonded together
What are carbohydrates?
They are organic molecules made of C, H and O. They are biologically relevant e.g. starch and cellulose
Both of these are polymers made of glucose (other carbohydrate) monomers.
Their structures differ in the way the glucose molecules are joined together
What is DNA? Describe its role and structure
DNA = deoxyribonucleic acid
It is the material that makes up chromosomes – cell structures that store genetic information
DNA is made of two polymer chains that are held together in a double helix
Each polymer chain can be made from 4 different monomers - nucleotides
