Chem Past Paper -2 Flashcards
What colour flame would sodium ions produce
Yellow
Name a metal ion that would produce a green flame
Copper
Some fireworks contain a mixture of metal ions. Why is it difficult to identify the metal ions from the colour of the flames
Colours are masked
Silver nitrate solution and dilute nitric acid are added t the solution. A cream precipitate forms. Which ion s shown to be present by the cream precipitate
Bromide
Descrive a test to show the presence ofsulfate ions in the solution. Give the result of the test if there are suklflate ions in the solution
add barium chloride (solution) add hydrochloric acid
white precipitate produced
What name is given to a useful prodcut such as methylated spirit
Formulation
Suggest why pyridine 9unpleasant spell0 and methyl violet (make mixture purple) to make methylated spirit
To deter consumption/drinking by people
Uses of methylated spirit
Fuel
Solvent
Antiseptic
Describe how ethanol is produced from sugar soluton
Give the name of this process
Fermentation
Add yeast
Anaerobic conditions
Warm
Name the gas produced when sodium is added to ethanol
Hydrogen
Methanol is used to prodcue methanoic acid, what tupe of subtance reacts with methanol to produce methanoic acid
Oxidising agent
Give the approximate temp used in haber process
450 C
Pressure used in haber process
200 atm
The mixture of gases from the reactor cools in the condensor
Suggest why ammonia condenses but the other gases do not
Ammonia has a higher bp
Why are scientist not certain about the percentage of each gas in the earth early atmosphere
Occured 4.6 bn years ago
Limited or no evidence
What is the problem in chromatography when line drawn in ink
Ink dissolves
Ink runs in solvent/water
What is the problem with water used in chromatography
Colour will not dissolve/move
Polyesters are produced when monomers join togetehr and lose a small molecule. Name this small molecule
Water
Why is a mixture of poly(propene) and wool is used to make carpets is more sustainable than using just one of the materials
poly(propene) comes from a non-renewable source • poly(propene) requires a lot of energy to make • poly(propene) is not biodegradable • a wool carpet needs replacing more often • wool requires the use of large areas of land (which could be used to grow food crops)
Explain how carbon monoxide is produced when petrol is bruned in car engine
Incomplete combustion
Insufficenient limited o2 supply
Suggest two reasons why maximum allowed percentage of carbonn monoxide has been decreased for newer cars
carbon monoxide toxic /
poisonous
• greater public concern / awareness about pollution
• more cars so otherwise there would be more carbon monoxide entering atmosphere
• improved engine technology
• catalytic converters have been introduced
Give one reason for having a max allowed prcentage of unburned hydrocarbons in exhaust fumes
Reduce health problems
Reduce global dimming
Give two effects of atmospheric pollution which are reduced by using catalystic converters
- acid rain
- respiratory problems
- carbon monoxide
- global dimming/smog
The catalyst in catalytic converters is a mixture in three elements. Where is the periodic table are these elements most likely to be found
Transition metals
Explainwhat happens to the yield of methanol if a temo higher than 250 is used
Smaller yield
Favours endothermic reaction
Sugggest why a catalyst is used in this industrial process
Less energy needed
Sugest the effect of using the catalyst on the equilibrium yield of methanol
No effect/change
Melamine is a ppolymer used to make non-disposable cups
Melamine does not melt when it is heated
Why
Thermosetting polymer Contains crosslinks (between polymer chains)
Suggest a suitable temp for the furnace in fractional distillation
Betwee 400-500
Suggest two reasons why bitumen is not used as fuel
- too viscous
- not very flammable
- bp too high
Conditions needed to crack hydrocarbon molecules from the diesel oil fraction
- high temp
- steam
- catalyst
Explain why large hydrocarbons cracked into smaller
- greater demand
- smaller
- more uselful, better fuel, used to make alkenes, used to make polymers
How to show presence of lithium ions experiment
crush tablets or dissolve tablet (in water or acid) • clean wire
• place on wire
• place in (roaring / blue / non-luminous) flame
• observe flame colour
• crimsonflame
What two pieces of meaasuring apparatus could the student use to fidn the rate of production of hydrogen gas
- gas syringe
- stopclock/stopwatch
Magnesium is fixed to some steel ships. Explain how this prevents the steel from rusting
- mg more reactibe
- provides sacraficial protection
Explain why aluminium windowframes do not corrode after they are made
- al has coating of aluminium oxide
- protects metal from further corrosion
Suggest reasons why wood is more sustainable than natural gas as a fuel for central heating boilers
wood is renewable
or
(natural) gas is finite
(burning) wood produces the same amount of carbon dioxide as the trees absorbed
or
(burning natural) gas increases the amount of carbon dioxide (in the atmosphere
Name the function group of -COOH
Carboxylic acid
Monomer -OH and -COOH join to produce a polyester and small molecule - what is it
Water
Why does this type of polyester melt when it is heated
- thermosoftening
- no cross-links
Suggest why an outer skin is added to a polysester surf board
Make it -harder -stronger tougher -waterproof
Describe a test to show that the drinking water contained aluminium ions
add sodium hydroxide (solution to water sample)
white precipitate (forms)
(precipitate which is) soluble in excess (NaOH)
Plan an nvestigation to find the amss of dissolved solis in a fixed vollume of water
weigh (evaporating) basin / dish
• add measured volume of water
• weigh (evaporating) basin / dish and water
• heat to evaporate water
• reweigh
• repeat heating until constant mass obtained
• subtract mass of (evaporating) basin / dish from mass
• repeat and calculate a mean, discarding anomalous results • calculate the mass in 100 cm3 water if necessary
Explain why organisms could not have evolved same way on titan as on earth- low o2 and co2 conc
Titan has) little / no oxygen
(so) photosynthesis has not occurred (on Titan)
(therefore) little / no carbon dioxide present (on Titan)
or
(therefore) oxygen-using animals cannot have evolved (on Titan)
Explaine how methane a greenhouse gas, keeps titan warmer than otehr moons that do not have atmosphere
methane) allows short(er) wavelength radiation to pass through (from the sun)
(which is) re-emitted from the surface as long(er) wavelength radiation
(which is) absorbed (by methane in the atmosphere
Why is a greater pressure not used in the haber process
• the energy costs would be
high(er)
• the equipment would need to be strong(er)
• high(er) pressures are (more) dangerous
To test for sulfate ions the student added dilute hcl to copper sulfate solution. Name the solutio that would hsow the presence of sulfate ions when added to this micture
Barium chloride
Why filter water
Remove undisolved solids
How is liquid effluent processed
Aerobic biological treatment
How is solid sewage sludge proposed
Anaerobic digestion
Suggest reason why the total mass of processed solid sewage sludge increased between two dates
• the population increased
• more waste water produced • less untreated sewage
discharged
Between 1992 and 2010 the proportion of processed solid sewage sludge used as fertiliser increased. Suggest why
- increased demand for food (due to incrasing pop)
- conserve energy/resources
- landfill space is running out
- increased demand for organic fertiliser
Compare two molecules n term of
Structure and bonding
Their reactions
- no. Atoms
- no. Bonds
- size of molecule
- conbustion
- reactions- addition
Which was could one increase the distance between the spots
- allow solvent front to travel further
- use a diff solvent
The manufacturers of greeen ink always use the same proportions of yellow dye and blue dye. Suggest why
-so that shade of green is the same
Or- green ink is a formulation
What will def produce a smaller rf value if the solvent and paper are both changed
- dye less soluble in new solvent
- more attracted new paper
Describe how ceramic food plates are produced from clay
- clay is shapes
- heated in furnace
Ethanoic acid ionises in water
CH3COOH(aq) CH3COO-(aq) + H+(aq)
- incomplete/partial ionisation
- reaction is reversible
Methaoic acid
HCOOH
CH3CH2COOH
Propanoic aci
Give name of the ester produced when ethanoic acid reacts when ethanol
Ethyl ethanoate
The student concluded that the large calcium carbonate lumps reacted more slowly than the small calcium carbonate lumps. How do the students result show that this conclusion is correct?
(for large lumps) a smaller number of moles of gas is collected in the same time or
(for large lumps) more time is needed to collect the same number of moles of gas
or
the line (of best fit for large lumps) is less steep
Glycine reacts by condensation polymerisation to produce a polypetide and one other substance. Name other substance produced
Water
Which gases from earths early atmosphere could have produced this element glycine for algea
Ammonia
Nitrogen
Describe the shape and structure of dna
two polymer chains
four (different) monomers / nucleotides
(double) helix
Give the name of the solvent used to dssolve the ions in this reaction
Water
Explain why a change in pressure doesnt affect the colour of the equilibrium mixture
no change in equilibrium position
(because) no gases are present
Suggest why uisng solar energy is a more suistainable way of generating electricity than burning oil
Solar is renewable source of energy
solar energy may nit be able to replace the generation of electricity from fossil fuels completely? Suggestwhy
- sunshine unreliable
- increased demand for enrgy
- lack of space
Each student did the chomatography investigation differently. Rf values diff. How did the investigations differ
Dff solvent used
What is the stationary phase in paper chromatography
Paper
How can diff forms of poly(ethene) be produced from ethene
-use diff reaction conditions
Explain why HDPE has a higher densiity than LDPE
HDPE polymer chains/ molecules are closer together
-more atoms per unit volume
Name soluble salt produced when calcium phosphate reacts w/ nitric acid
Calcium nitrate
Name soluble salt produced when calcium phosphate reacts w/ phosphoric acid
Triple superphosphate
Suggest reasons why recylcling scrap copper is a more ssustainable way of obtaining copper than processing copper ores
recycling conserves copper ores
• recycling uses less energy
• recycling reduces waste
• mining / quarrying cause environmental impacts
Describe how copper is extracted from low grade ores by phytoming
grow plants (on land containing copper ores)
plants are burnt (to produce ash)
ash dissolved in acid (to produce a solution of a copper compound)
electrolysis of solution (containing a copper compound) or
displacement (of copper) from solution (containing a copper compound)
Ohytomining has not been widely used to extract copper - suggest why
high grade ores still available • land not available
• phytomining takes a long time • new technology
Explain why the lines of best fit become horizontal
- reactionhas stopped
- reactant is used up
The activation energy for the reaction between zinc and sulfuric acid is lowered if a solution containinng meal ions is added. What is the most likely formula of. metal ions added
CU2+
Describe conditions needed for cracking
- high temp
- steam/catalyst
Butanil can be produced from sugar solution by adding bacteria. Sugar solution is broken down in similar ways by bacteria and by yeast
Suggest reaction conditions needed
- warm
- anaerobic conditions
