topic 7:organic chemistry Flashcards
What is crude oil?
crude oil is a mixture of compound; fossil fuel consisting of the remains of ancient biomass
Finite resource – cannot be replaced as it is used up
What is a hydrocarbon?
A compound made up exclusively of hydrogen and carbon atoms
What are alkanes?
saturated hydrocarbons of a general formula C n H 2n+2
What is a homologous series?
Series of compounds with the 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
In general boiling points and viscosity increases 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
-Vapour rises up the fractionating column
-The column is hotter at the bottom and cooler at the top
-Hydrocarbons as they go up the column and condensed at different height, 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 vapour, passed over a hot catalyst or heated to vapour, mixed with steam and heated to high temperatures
How are the 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 changes occur 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 bomb becomes a single carbon – carbon bond
a) with hydrogen-hydro generation; requires a high temperature and a nickel catalyst
b) with steam-hydration; requires high temperature, pressure and concentrated phosphoric acid as a catalyst
c)with Br2/Cl2/I2
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 acid in presence of acid catalyst to form Esther
Oxidation of the alcohol leads to
carboxylic acids
What are some uses of alcohols?
fuels,solvents,drinks
State the conditions required for fermentation of glucose and state the equation of the reaction
30°C, aqueous solution of the glucose, absence of air, yeast added
C6H12O6 —-> 2 CH3 CH2 OH + 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 carbonates to form carbon dioxide
-React with alcohol within an acid catalyst produce Esters
-React with metals to give off hydrogen gas
what type of acid is carboxylic ackd
it is a weak acid
Explain my carboxylic acids are weak acids
they are partially dissociated in water, thus the pH of carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration
