Practice questions Flashcards
Plan an investigation to determine the Rf value for the dye in this food colouring
- Draw a pencil start line on the chromatography paper and place spot of food colouring on the start line
- Use a suitable solvent and place the solvent in the beaker
- Place chromatography paper in the beaker so that it is in the solvent but the solvent is below the start line
- Use a lid and wait for the solvent to travel up the paper
- Mark the solvent front and dry the chromatography paper
- Measure distance from the start line to the solvent front
- Measure the distance between the start line and the centre of the spot
- Use these measurements to determine the Rf value
What is the stationary phase in paper chromatography?
Paper
What is the mobile phase in paper chromatography?
Solvent
Which will definitely produce a smaller Rf value if the solvent and paper are both changed?
The dye is less soluble in the new solvent and more attracted to the new paper
What is a pure substance in chemistry?
A single element or a single compound
What is a pure substance in everyday life?
A substance that has had nothing added to it
What is the test for chlorine gas?
Damp litmus paper turns white
Explain how the different dyes in X are separated by paper chromatography
- Solvent moves through the paper
- Different dyes have different solubilities in the solvent
- And different attractions to the paper
- So they are carried different distances
describe the conditions needed to crack hydrocarbon molecules from the diesel oil fraction
- high temperature
- steam or a catalyst
explain why large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules
- greater demand for smaller hydrocarbon molecules
- because they are more useful
suggest two reasons why wood is more sustainable than natural gas as a fuel for central heating boilers
- wood is renewable
- wood is carbon-neutral, burning wood produces the same amount of carbon dioxide as the trees absorbed
explain the process by which carbon monoxide can be produced when methane is burned
- incomplete combustion
- due to insufficient oxygen
name the source of the oxygen needed to burn fuels
air
explain why octane is a hydrocarbon
it is a compound containing only hydrogen and carbon
explain how alkenes are produced using fractional distillation followed by cracking
- crude oil is vaporised and fed into the bottom of the fractionating column
- temperature decreases going up the column
- fractions have different boiling ranges
- fractions condense and are collected once they reach the temperature of their boiling point
- heavier fractions are collected at the bottom and lighter fractions are collected at the top
- heavier fractions are collected and undergo cracking at high temperatures and in the presence of either steam or a catalyst
- large molecules split into smaller molecules to produce a mixture of alkenes and alkanes
what is the environmental impact of nitrogen oxides?
acid rain
what is the environmental impact of particulate matter?
global dimming
what are two possible reasons why the percentage yield of ethanol is less than 100%?
- some ethanol changes back into ethene and steam
- some ethanol escapes from the apparatus
give two advantages and two disadvantages of using fermentation to produce ethanol
advantages:
- uses sugar cane which is a renewable source
- can be carried out at room temperature so uses a low amount of energy
disadvantages:
- produces impure ethanol
- slow rate of reaction
describe a test for the double carbon-carbon bond in cycloalkane molecules
test: bromine water
result: bromine water turns from orange to colourless
suggest the reaction conditions needed to produce butanol from sugar solution by adding bacteria
- room temperature
- anaerobic conditions
what type of substance is ethanol when used to remove grass stains?
a solvent
what is added to grape juice to cause fermentation?
yeast
what is the name of the ester produced when ethanol reacts with ethanoic acid?
ethyl ethanoate
describe how ethanol is produced from sugar solution (3 marks)
- fermentation
- yeast is added to sugar solution
- anaerobic conditions
name the gas produced when sodium is added to ethanol
hydrogen
what type of substance reacts with methanol to produce methanoic acid?
oxidising agent
explain how oxidation causes the wine to taste of vinegar after a few days
- air contains oxygen
- which oxidises the ethanol
- to produce ethanoic acid
what materials are used to make glass?
- sand
- limestone
- sodium carbonate
why is an alloy used instead of pure aluminium to make window frames?
an alloy is harder than pure aluminium
suggest why poly(ethene) a thermosoftening polymer is easier to recycle than thermosetting polymers
- poly(ethene) melts
- so can be reshaped into new products
how can different forms of poly(ethene) be produced from ethene?
use different reaction conditions
describe the flame emission spectroscopy
- used for identifying metal ions in solution or measuring their concentration
- the sample is put into a flame and the light given out is passed though a spectroscope
- spectroscope measures the exact wavelength of light emitted by a metal ion, allows for definite identification
- concentrations are found by measuring the intensity of the light emitted
- the more intense the light, the greater the concentration of the metal ion in a solution
water obtained by distillation does not need to be sterilised and is safe to drink, suggest why
distilled water is pure
how is fresh water sterilised? (2 marks)
- using chlorine
- using ozone
what is the pH of fresh water?
pH 7
Oil contains carbon and some sulfur. When oil is burned, the products of combustion may be released into the atmosphere. Explain the environmental effects of releasing these products of combustion into the atmosphere.
- complete combustion of carbon releases carbon dioxide
- which is a greenhouse gas and causes surface temperature to increase
- therefore contributes to global warming
- can lead to issues such as: sea levels rising, reduced biodiversity, flooding, droughts etc
- incomplete combustion of carbon releases carbon monoxide and soot
- carbon monoxide which is toxic
- soot causes global dimming and respiratory problems in humans
- combustion of sulphur releases sulphur dioxide
- which causes acid rain
suggest one reason why using solar energy is a more sustainable way of generating electricity than burning oil
solar is a renewable source of energy
solar energy may not be able to replace the generation of electricity from fossil fuels completely, suggest two reasons why.
- sunshine is unreliable
- increased demand for energy
- lack of space for solar panels
suggest three reasons why recycling scrap copper is a more sustainable way of obtaining copper than processing copper ores.
- copper ore is finite, recycling conserves copper ore
- less energy required for recycling
- recycling reduces waste
describe how copper is extracted from low-grade ores by phytomining (4 marks)
- plants are grown on land containing copper ores
- plants are burnt to produce ash
- ash is dissolved in acid to produce a solution of a copper compound
- electrolysis of solution to obtain copper
phytomining has not been widely used to extract copper, suggest two reasons why
- takes a long time
- no land available
- new technology
- high grade ores are still available
explain how potable water is produced from fresh water (4 marks)
- fresh water is collected from an appropriate source such as a river
- the water is passed through filter beds
- to remove undissolved solids
- the water is then sterilised using chlorine
- which destroys harmful microbes
which three properties of carbon monoxide make it necessary to use carbon monoxide detectors?
- colourless
- odourless
- toxic
name the substance removed from seawater by desalination
salt/sodium chloride
desalination requires large amounts of energy, desalination is only used when there is no other source of potable water, give one reason why.
it is expensive
why is the water filtered?
to remove undissolved solids
why is chlorine gas used to treat water?
to sterilise the water
describe a test for chlorine gas, give the result of the test if chlorine is present.
test: damp litmus paper
result: paper gets bleached white
explain why it is more difficult to produce drinking water from waste water than from water in lakes
- water needs more processes
- more microbes in waste water
- and more organic matter
- contains toxic chemicals
How could the water be tested to show it is pure? Give the expected result of the test for pure water.
- determine boiling point
- should be at a fixed temperature of 100 degrees
why is producing drinking water from sea water expensive?
high energy requirement
paper plates are biodegradable and recyclable, which stage of a life cycle assessment (LCA) would contain this information?
disposal at the end of useful life
which two processes are used to make ceramic plates?
- shaping wet clay
- heating in a furnace
why does a thermosetting polymer behave differently to a thermosoftening when heated? You should refer to crosslinks in your answer.
thermosetting polymers have crosslinks between polymer chains, thermosoftening polymers have no crosslinks
suggest two pieces of information about energy usage which would help to produce a complete life cycle assessment (LCA) for the three food plate materials
- energy used in transportation
- energy used in extraction of raw materials
describe how ceramic food plates are produced from clay
- wet clay is shaped
- and heated in a furnace
which type of bonding is present in small alkene molecules?
covalent
which process is used to make poly(styrene) from small molecules?
polymerisation
