T7 organic chemistry Flashcards
what is crude oil
mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
finite resource - can’t be replaced as it is used up
what is a hydrocarbon
compound made up exclusively of hydrogen and carbon atoms
what are alkanes
saturated hydrocarbons of a general formula
CnH2n+2 (where n is the number of carbon atoms in the molecule).
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
- in general, 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 the fractionating column
- column is hotter at bottom
- 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 bottom
- 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 the products of cracking used
products are alkanes and alkenes - used as polymers and starting materials for synthesis
what is an alkene
unsaturated hydrocarbon, contain C=C bond
general formula CnH2n
what is the test for alkenes
add bromine water
colour change occurs from orange to colourless
describe the combustion of alkenes
burn with smoky flames due to incomplete combustion
describe addition reactions of alkenes
additions atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond
a. with hydrogen - hydrogenation; requires a higher temperature and a nickel catalyst
b. with steam - hydration; requires high temperature, pressure and concentrated phosphoric acid (H3PO4) as a catalyst
c. with Br2/Cl2/I2 - addition of halogens
what is an alcohol
organic compound that contains and -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
what are some uses of alcohols
fuels
solvents
drinks
state the conditions required for fermentation of glucose and state the equation of the reaction
30C, aqueous solution of the glucose, absence of air, yeast added
C6H12O6 > 2CH3CH2OH + 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 alcohols with an acid catalyst to produce esters
- react with metals to give off hydrogen gas
what type of acid is carboxylic acid
weak aid
explain why carboxylic acids are weak acids
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
