Paper 2 Knowledge Gaps: Content Flashcards
How is ethanol produced?
Through fermentation
How is ethanol concentrated?
fractional distillation
Write a word equation for fermentation
Glucose –> ethanol + carbon dioxide
What is the formula for ethanol?
C2H50H
Where do the enzymes for fermentation come from?
From yeast cells
State a quick overview of what happens in fermentation
Sugar or starch is dissolved in water and yeast is added
What do the enzymes do in fermentation?
They break down the sugars to alcohol
What does chemically oxidised alcohol produce?
Carboxylic acids
Why must there be an air lock to ferment the ethanol?
To keep the oxygen out as yeast fermentation is a type of anaerobic respiration
What is the highest concentration of alcohol produced by yeast fermentation?
15%
Explain how fractional distillation is used to produce more concentrated solutions of alcohol such as ethanol
- The water and ethanol solution are heated
- Ethanol evaporates first as it has a lower boiling point than water, cools then condenses
- The water left evaporates, cools then condenses
Write a balanced equation for the formation of ethanol from carbohydrates
C6H12O6 + enzymes → 2CO2 + 2C2H5OH
What is the general formula of a carboxylic acid?
Cn-1H2n+1COOH
State the chemical properties of alcohol
- Produce carbon dioxide and water during complete combustion
- can be oxidised to form carboxylic acids
- react with reactive metals, forming water as one of the products
Define addition polymerisation
A type of polymerisation in which the monomers add onto each other and no small molecule is eliminated. It only occurs with monomers that contain the double C bond
How do ethene molecules join together to form poly(ethene)?
- They lose the carbon double bond
- which then transfers to the sides of each of the carbons
to form a repeating unit
How do we deduce the structure of a monomer from the polymer?
- Identify the repeating unit in the polymer
- Change the single bond in the repeat unit to a double bond in the monomer
- Remove the bond from each end of the repeat unit and the subscript n (which can be placed in front of the monomer)
Define condensation polymerisation
A small molecule is formed as a byproduct each time a bond forms between two monomers
What are the uses of poly(tetrafluoroethene)?
- nonstick coating for frying pans
- burette taps
- stain proof clothing
What are the properties of poly(tetrafluoroethene)?
- tough
- slippery
What are the uses of poly(chloroethene)?
- window frames
- gutters
- pipes
What are the properties of poly(chloroethene)?
- tough
- good insulator
- rigid
- flexible
What are the uses of poly(propene)?
- buckets
- food packaging
- ropes
What are the uses of poly(ethene)?
- plastic bags and bottles
- cling film
What are the properties of poly(propene)?
- flexible
- shatterproof
- strong
What are the properties of poly (ethene)?
- flexible
- cheap
- good insulator
What products are produced during the condensation reaction between an alcohol and a carboxylic acid?
Esters and water
What particular position must the two monomers be whilst reacting under condensation polymerisation?
functional monomers must be facing each other so that the ester link can be formed between the carbon and oxygen and water can be removed
What is the general formula of alcohol?
CnH2n+1OH.
Describe how to carry out a hydroxide precipitate test
- Place a little of the unknown solution in a test tube and add a few drops of dilute sodium hydroxide solution. Record any observations
- If a white precipitate forms, add an excess of sodium hydroxide and record any observations
What is the hydroxide precipitate test carried out for?
- Place a little of the unknown solution in a test tube and add a few drops of dilute sodium hydroxide solution. Record any observations
- If a white precipitate forms, add an excess of sodium hydroxide and record any observations
What is the effect of adding sodium hydroxide to aluminium?
Forms a white precipitate, dissolves in excess NaOH to form a colourless solution
What is the effect of adding sodium hydroxide to calcium?
White precipitate, insoluble, so remains in excess sodium hydroxide
What is the effect of adding sodium hydroxide to copper?
Light blue precipitate, insoluble in excess
What is the effect of adding sodium hydroxide to iron II?
Green precipitate, insoluble in excess
What is the effect of adding sodium hydroxide to iron III?
Red-brown precipitate, insoluble in excess
How can we test for ammonium ions using sodium hydroxide?
- Gently heat the solution after adding the NaOH
- If ammonium ion is present, it produces ammonium gas and can be tested with red litmus paper
Describe the test for ammonia using HCl
- React the gas with HCl
- A white smoke is produced if ammonium gas is present of ammonium chloride
How can we test for the presence of a carbonate ion?
Bubble the gas through limewater or any dilute acid. If the limwater goes cloudy, it indicates the presence of CO2
How can we test for the presence of a sulfate ion?
- Add dilute HCl followed by a barium chloride solution
- A white precipitate of barium sulfate will form when sulfate ions are in the solution
How can we test for the presence of halide ions?
- Add dilute nitric acid followed by the addition of silver nitrate solution
- This will form a silver halide precipitate
- Depending on the halide present, a different colour precipitate is formed, allowing us to identify the halide ion
What colour does chloride turn when added to a silver precipitate?
White
What colour does bromide turn when added to a silver precipitate?
Cream
What colour does iodine turn when added to a silver precipitate?
Yellow
How is cataylitic cracking carried out?
- crude oil fractions are heated to evaporate them
- vapours are passed over a catalyst containing aluminium oxides
- this breaks the covalent bonds when they come into contact with the surface of the catalyst, causing thermal decomposition reactions
- this produces a random selection of alkanes and alkenes
How is steam/thermal cracking carried out?
- process carried out similar to catalytic cracking, but at higher temperatures
- vapourised hydrocarbons are mixed with steam and heated to a high temperature, which induces cracking
What is natural gas used for?
Domestic heating and cooking
What is petrol used for?
Fuels for cars
What is kerosene used for?
Jet fuel
What is diesel used for?
Fuel for some cars and trains
What is fuel oil used for?
Ships and power station
What is bitumen used for?
Surfacing roads and roofs
