Organic chemistry pt 1 (Hydrocarbons - fermentation) Flashcards
Hydrocarbons, Alkanes, alkenes, fractional distillation, cracking, alcohols, fermentation
What is crude oil? (3)
- a finite resource found in rocks
- the remains of ancient biomass consisting mainly of plankton that was buried in mud
- a mixture of very large hydrocarbons
Most of the hydrocarbons in crude oil are ________
alkanes
The larger the hydrocarbon: (4)
- the more viscous it is
- higher its boiling point
- less volatile it is
- less flammable
the equation for the combustion of hydrocarbon
hydrogen + oxygen = carbon dioxide + water (+ energy)
During the combustion of hydrocarbon, carbon and hydrogen are …….
oxidised
The general formula for alkanes
CnH2n+2
Alkanes are : (2)
- saturated compounds
- unreactive but burn well
the first four alkanes
Methane, ethane, propane, butane
Mary Eats Pickled Beetroot
Why is there a greater demand for shorter- chain alkanes and carbons as fuels?
because they release energy more quickly by burning
because they are easy to ignite and have low boiling points
What does each fraction in fractional distillation contain?
hydrocarbon molecules with a similar number of carbon atoms
What is the process of fractional distillation?
1) crude oil is heated until it evaporates
2) the vapour moves up the fractionating column
- longer hydrocarbons have high boiling points so they condense back into liquids near the bottom
- shorter hydrocarbons have low boiling points so they are near the top
3) end up with the crude oil mixture separated out into different fractions
What can the fractions in fractional distillation be processed to produce?
fuels and feedstock for the petrochemical industry
What fuels are produced in crude oil
petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases
What is produced by the petrochemical industry?
solvents, lubricants, polymers, detergents
What happens when combustion is not complete?
CO, unburnt fuels and solid particles containing soot may be released
what is carbon monoxide?
a colourless, odourless, toxic gas
How do particulates impact the environment?
cause global dimming by reducing the amount of sunlight reaching the Earth’s surface and cause damage to people’s lungs
How is nitrogen oxide formed and what is the effect of it on people and the environment?
due to high temperatures when fuels burn, nitrogen in the air can react with oxygen to form nitrogen oxide these gases can cause respiratory problems in people and from acid rain. which damages plants and buildings
What is cracking?
when longer-chain hydrocarbons are broken down into shorter useful hydrocarbons
Shorter hydrocarbons are _________ reactive than Longer-chain hydrocarbons
more
What is the process for catalytic cracking?
1) liquid long-chain hydrocarbons are soaked in ceramic wool so it won’t mix with the catalyst and are heated so they are vapourised
2) The vapour will then be passed over a hot powdered aluminium oxide or silicon dioxide
3) the long-chain molecules split apart on the surface of the specks of the catalyst
What is the process for steam cracking?
1) vapourised hydrocarbons are mixed with steam
2) they are then heated at a high temperature
What are the products of cracking long-chain alkanes?
short chain alkanes and alkenes.
Features of Alkenes?
- unsaturated hydrocarbons as there is a carbon double bond
- more reactive than alkanes as more atoms can easily be added to the carbons at the double bond
What are the first four alkenes
ethene, propene, butene, pentene
What is the formula for combustion for alkenes and describe how they burn?
alkene + oxygen
=
carbon + carbon monoxide + carbon dioxide + water
they tend to burn with smokier flames than alkanes due to incomplete combustion
What is an addition reaction?
when carbon- carbon double bond opens up to leave a single bond and a new atom is added to each carbon
What are the different types of addition reactions for alkenes?
- reaction with steam (hydration)
- reaction with bromine and ethene
- hydrogenation
- reaction with halogens
What is hydrogenation and what is needed in it?
the addition of hydrogen to an alkene which produces an alkane
- nickel catalyst
- a temperature of 150 degrees is needed
What happens when halogens react with alkenes?
the molecules formed become saturated with the carbon double bond each becoming bonded to a halogen atom
what is the product of bromine and ethene?
name the chemical formula and draw it
what time of reaction is this
dibromoethane
C2H4Br2
addition reaction
How do you test for alkenes?
when bromine water is added to an alkane, no reaction will happen and it’ll stay bright orange
when added to an alkene it will turn colourless
What are alcohols?
carbon-based molecules that contain the functional group, hydroxyl,
-OH
What is the first four alcohols in the homologous series: hydroxyl
Methanol, Ethanol, Propanol, Butanol
What is the General formula for alcohols?
CnH2n+1OH
What are the features for alcohols?
** what happens to alcohol in water
what happens when it reacts with sodium
what do alcohols produce during combustion
what are they used as
what happens when they react with oxidising agents?
- dissolve in water to form neutral solutions
- react with sodium to produce hydrogen
- burn in air to produce carbon dioxide + water
- are used as fuels and solvents
- they react with oxidising agents to form carboxylic acids and water
What is fermentation?
a chemical reaction in which ethanol and carbon dioxide are produced from glucose mixed with yeast
what is the equation for fermentation?
sugar —–> ethanol + CO2
What is the optimum conditions for fermentation to work at?
37 degrees ( warm temperature
slightly acidic solutions
under anaerobic conditions
yeast
What happens if the temperatures are too high or too low during fermentation?
too low: the yeast becomes inactive and the rate of reaction slows
too high: the yeat is denatured and stops working
Advantages and disadvantages to fermentation?
Pros :
- low temp = less energy
- glucose is from plant = renewable
Cons :
- ethanol produced is in an aqueous solution = purified by distillation = high energy
Pros and cons of making ethanol with hydrogenation
pros :
- high yield
cons :
- high temperature = more energy
What is the product of hyrdogenation?
Describe
double double carbon bond in the alkene becomes single and two hydrogen atoms are added onto the ends
an alkane is made
What is hydration?
What are the conditions and productions?
reacting alkene with water = addition reaction
Ethene + water (must be steam) —> ethanol
300 degrees celsius and 70 atms
phosphoric acid as catalyst
