Exam questions Flashcards
two characteristics of a homologous series (2)
- general formula
- similar chemical properties
suggest why the branched chain isomer shown above has a lower boiling point? (2)
- less surface area
- weaker van der waals
state what is meant by the term stereoisomers (2)
- same structural formula
- different orentation
explain how these oxides of nitrogen are formed (2)
when there is a spark and a high-temperature nitrogen and oxygen in the air bond together
Nucleophile (1)
electron pair donator
substitution, as applied to nucleophilic substitution in a haloalkane (1)
halogen is substituted
hydrolysis (1)
splitting molecules using water
describe how ions are formed in a time of flight mass spectrometer (2)
- high voltage is applied to the sample
- element vapourised into gas
- electron knock out or orbit
a mass spectrometer can be used to determine the relative molecular mass of molecular substances.
explain why it is necessary to ionise molecules when measuring their mass in a mass spectrometer (2)
- ions are accelerated by an electric field
- only ions will create a current when they hit the plate
outline how the mass spectrometer is able to separate two species to give two peaks (4)
- positive ion accelerates by an electric field
- to a constant kinetic energy
- lighter ions travel quicker
- so will be detected first
why is the first ionisation energy of Krypton is greater than that of bromine (1)
more protons than bromine
in 1963, Krypton was found to react with fluorine. state why this discovery was unexpected
krypton is a noble gas
Describe how ions are formed in time of flight mass spectrometer
Element go into the mass spectrometer and are bombarded with electron which knocks the electron out of orbit making it a positive ion. High voltage is applied to the sample
The element is vaporised into a gas
Mass spectrometer can be used to determine the relative molecular mass of molecular substance
Explain why it is necessary to ionise molecules when measuring their mass in a mass spectometer
Ions are accelerated by an electric field
Only ions will create a current when they hit the plate
Outline how the TOF mass spectrometer is able to separate two species to give two peaks
Positive ion accelerate by an electric field
To constant kinetic energy
Lighter ion travels quicker
So will be detected first
Define the term relative atomic mass
Average mass of one atom / (1/12) of a carbon 12 atom
State why the isotope 10B and 11B have similar chemical reactions
Same number of electrons
Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron
You have to remove an electron from a positive ion which requires more energy
Give one reason why the second ionisation energy of silicon is lower than the second ionisation energy of aluminium
You have to remove an electron from a shell (3p orbital) needs more energy shell than the ‘s’ shell
State the type of reaction that occurs when calcium carbonate reacts with nitric acid
Neutralisation
Explain why the melting point of sodium chloride is high
Strong electrostatic attraction between the positive and negative ions, you need a lot of heat to overcome the forces
Name the type of bonding in sodium chloride
Ionic
Suggest why the melting point if sodium iodide is lower than the melting point of sodium bromide
Iodide is lower on the periodic table than sodium so its less reactive
What is the formula of calcium nitrate (IV)
A CaNO3
B Ca(NO3)2
C Ca2NO2
D Ca(NO2)2
B
State the meaning of the term covalent bond
Chemical bond where a pair of electrons are shared between two atoms
BF4-
Name the type of bond formed when a molecule of BF3 reacts with an F- ion. Explain how the bond is formed
Co-ordinate bonding
The 4 fluorine shares its electrons with boron but that fluorine hasn’t lot a full outer shell so has a negative charge
Explain why nickel has a high melting point
They are strong because a lot of force has to be used to overcome the force of attraction between electron and positive ions
Explain why nickel is ductile
Its layers can side over each other
Define the term electronegativity
The power of the atom to attract an electron in a covalent bond
Explain how the strongest type of intermolecular force in liquid HF arises
Large difference in electronegativity between H and F and there is a dipole formed which are then attracted into each other
Explain the trend in the boiling points of hydrogen halides from HCl and HI
Van der waals
Increasing size
Give one reason why the boiling point of HF is higher than that of all the other hydrogen halides
Hydrogen bonding needs more energy to break the bonds
Iodine and diamond are both crystalline solids at room temperature. Identify one similarity in the bonding, and one difference in the structure of these two solids. Explain why these two solids have very different melting points
Iodine
Covalent bonds
Molecular
Weak van der waals forces
Diamond
Giant molecular
Covalent bonds
Higher melting point
Predict the shape of the AlH4-
Explain why it has this shape
Tetrahedral
Equal repulsion form four bonding pairs
Outline how the mass spectrometer is able to separate these two species to give two peaks
The ion is accelerated by the electric field to a constant kinetic energy. One species would be lighter so would be detected first
Explain in the terms of electronegativity why the boiling point of H2S2 is lower than H2O2
Oxygen has a higher electronegativity change than sulphur
No hydrogen bonding
Describe the structure of and bonding in graphite and explain why the melting point of graphite is very high
Covalent bonds need a lot of energy to break
Graphite has layers
Have to break lots of bonds
Explain why iodine vaporises when heated gently
Weak intermolecular forces (weak van der waals) so not much energy is needed to break the bonds
State why iodine is a very poor conductor of electricity
No delocalised electrons
State two characteristics of a homologous series
General formula
Similar chemical properties
Suggest why the branched chain isomer shown above has a lower boiling point than octane
Less surface area
Van der waals
State what is meant by the term stereoisomers
Same structural formula
Different orientation
Suggest one improvement that would reduce errors due to heat loss in the student experiment ( p= mcΔt )
If you put a lid on the breaker so no gas can escape or heat
Give the meaning of the term mean bond enthalpy
Change in heat breaking the covalent bond
Give one reason why titanium is not extracted from titanium oxide using carbon
Product is brittle
Give the meaning of the term enthalpy change
Heat given out or taken in when bonds are broken at constant pressure
State hess’s law
Heat change at constant pressure
Define the term standard enthalpy of formation
When one mole of substance is bonded to form its elements with all reactants and products in their standard states
Explain the term mean bond enthalpy
The average bond enthalpy produced from different bonds ( enthalpy energy to break a covalent bond)
Define the term atomic number
Amount of protons in the nucleus
Explain why atoms of an element may have different mass number
Different number of neutrons
The first ionisation energy of krypton is greater than that of bromine
More protons than bromine
State and explain the trend in electronegativity values across period 3 from sodium to chlorine
It would increase
Number of protons increase in the same shell
Predict the type of crystal structure in solid zinc fluoride and explain why its melting point is high
Ionic
Strong electrostatic forces between ions so a lot of energy is needed to over come the electrostatic force between oppositely charged ions
Name the device used to ionise atoms in a mass spectrometer
Electron gun
BrF4- ions are also formed when potassium fluoride dissolves in liquid BrF3 to form KBrF4. explain in terms of bonding why KBrF4 has a high melting point
has a high melting point because of ionic bonding is strong because the electron aren’t shared between K+ and BrF4- are attracted to each other. strong electrostatic forces between oppositely charged ions creating on ionic lattice
state the strongest type of intermolecular force between hydrogen fluorine molecules
hydrogen bonding
the boiling points of fluorine and hydrogen Florine are low. explain why?
fluorine is covalently bonded together by weak van Waals forces where the hydrogen bonds are stronger than van waals
identify from the period 2 elements that has the largest atomic radius
lithium
state the general trend in first ionisation energies for the period 2 elements lithium to nitrogen
increases
identify the element that deviates from this general trend, from lithium to nitrogen, and explain your answer
Boron
electron removed from the 2p orbital which is higher in energy
explain in terms of structure and bonding why the melting point of carbon is high
giant molecular
strong covalent bonds
bonds must be broken
name a raw material from which hexane is obtained
crude oil
name the process used to obtain hexane from this raw material
fractional distillation
state the type of cracking that produces a high percentage of alkenes. state the conditions needed for this type of cracking
termal cracking
high temperature and high pressure
explain the main economic reason why alkanes are cracked
short-chain alkanes are more in demand so are worth more money than long-chained alkanes
identity a metal used as a catalyst in a catalytic converter. suggest one reason, other than cost, why the catalyst is coasted on a ceramic honeycomb
platinum
bigger surface area
suggest one reason why the yield of nitrogen dioxide formed during this reaction is often less than expected
decomposition not complete
by-products formed
suggest one reason why it is difficult to obtain a pure sample of nitrogen dioxide from this reaction
hard to separate the two gases
state the type of structural isomerism shown by but-1-ene and but-2-ene
positional
in industry, this fermentation reaction is carried out at 35 rather than 25. suggest a advantage and disadvantage
Ad= reaction would happen quicker Dis= uses more energy
state a condition of thermal cracking
high pressure and high temperature
the reaction is exothermic.
explain the effect of a change of temperature on both the position of equilibrium and the rate of reaction, and justify why a compromise temperature is used industrially
High temperature
- le chameliers principle predicts that equilibrium shifts to oppose any increase in temperature
- exothermic reaction
- high temperature= reduce yield
high temperature
- more high energy molecules
- more collisions
- rate of reaction increase
in a trial experiment the student failed to fill the burette correctly so that the gap between the tap and the tip of the burette still contained air. suggest what effect this would have on the measured volume of bromine water in this trial. explain your answer
- measured volume would be greater
- level in burette falls as the tap is filled before any liquid is delieved
other an not filling the bottom of the tap, suggest a reason for an inconsistency in the students results
drop size may vary
outline how the student could improve this practical procedure to determine the number of c=c double bonds in a molecule of the oil so that more consistent results are obtained
- larger single volume of oil
- dissolve oil
- transfer to conceal flask and make up 250cm3
- tritate (25cm3) sample from the flask
which statement about ethene is correct?
A- it has no geometric isomers because there is free rotation around the C=C bond
B-it reacts with HBr in a nucleophilic addition reaction
C-it burns in excess oxygen to produce carbon dioxide and water
D-the C=C bond is twice as strong as the C-C bond in ethane
C
what statement about ethanal is correct?
A-reacts with Tollens’ reagent to form silver
B-higher boiling point than ethanol
C-empirical and molecular formulas are different
D-belongs to a homologous series with general formula CnH2n+1O
A
which of these substances does not contribute to the greenhouse effect? A-unburned hydrocarbons B-carbon dioxide C-water vapour D-nitrogen
D
suggest a name for this type of reaction that iron(III) nitrate undergoes
thermal decomposition
suggest why the iron (III) oxide obtained is pure
other products are gases
explain, in terms of its structure and bonding, why nickel has a high melting point
nickel has a high melting point because its metallic bonded where there is a sea of delocalised electrons around the positive ions
explain why nickel is ductile
layers that can slide over each other
name the strongest attractive force between two ammonia molecules
hydrogen bonding
give the meaning of the term electronegativity
ability of an molecules to attract on electron pair in a covalent bond
oxides of nitrogen are also produced during the combustion of paraffin in air. explain how these oxides of nitrogen are formed
a spark in engine creates a high temperature where nitrogen an oxygen in the air
explain why the melting point of Dodecanese is higher than the melting point of the straight-chain alkane produced by cracking dodecane
melting point is higher because dodecane has more van Der Waals forces so if it has longer chains than more energy is needed so the melting point is higher
thallium bromide (TlBr) is a crystalline solid with a melting point of 480 degrees. suggest the type go bonding present in thallium (I) bromide and state why the melting point is high
ionic bonding
oppositely charged ions
strong attraction between ions
suggest one reason other than incomplete combustion or heat transfer to the atmosphere why the students value of enthalpy is different
heating in the container
the student said correctly that using a thermometer with an overall uncertainty for this experiment was ±0.25 was adequate for this experiment.
explain why this thermometer was adequate for this experiment
heat loss is a bigger uncertainty
octane and isooctane can be separated in the laboratory. name a laboratory technique that could be used to operate isooctane from a mixture of octane and isooctane
distillation
heat the mixture up
distilled off then condensed
explain how a catalyst works
provides an alternate route with a lower activation energy
platinum, palladium and rhodium are metals used inside catalytic converters. a very thin layer of the metals is used on a honeycomb ceramic support.
explain why a thin layer was used in this way
large surface area reduces cost (uses less money)
identify a reagent that could be used in a chemical test to show that oleic acid is unsaturated
state that would be observed in this test
bromine solution
orange to colourless
explain why 1,1,1-trifluoroethane does not lead to the depletion of the ozone in the upper atmosphere
C-F bond is strong
anti-bumping granules are placed in the flask when refluxing. suggest why these granules bumping
preventing vicious boiling
Magnesism oxide is a white solid with a higher melting point
Explain how the ions are held together in solid magnesium oxide
Electrons are transferred
Electrostatic attraction between charged ions
Addition polymerisation
Small unsaturated monors joined up by the opening of the double bond allowing them to join up to form a long carbon chain
What is meant by polymerisation
A chemical process that combines several monomers to form a polymer
Solvent molecules evaporate easily
Explain why substances made of simple molecules evaporate easily
They have weak forces between the molecules so they can be broken eaisly by putting only a small amount of energy put in
How does the number of atoms in one mole of argon compare with the number of molecules in one mole of ammonia?
Same
one mole of anything in the same
The equation for the decomposition of the hydrogen peroxide
2H2O2 ➡️ 2H2O + O2
State the measurement you would take in order to investigate the rate of this reaction
Measure the amount of gas given off at regular time intervals
Na2S2O3 + 2HCl ➡️ 2NaCl + S + SO2 +H2O
Identify the insoluble product of the reaction which forms the precipitate
Sulfur
Na2S2O3 + 2HCl ➡️ 2NaCl + S + SO2 +H2O
When this reaction takes place the collisions between the reacting particles requires an activation energy. State the meaning of activation energy
The minimum amount of energy needed for successful collisions
Explain why at a fixed temperature you might expect the react of the reaction to double when the concentration of sodium thiosulfate is doubled ans the concentration of hydrochloric acid remains the same
Na2S2O3 + 2HCl ➡️ 2NaCl + S + SO2 +H2O
High concentration means that there are double the amount of particles in a small space so that there is more likely to have twice as many for collisions
What is meant by the term rate of reaction
Change in concentration in unit time
On an maxwell Boltzmann graph
Why does the curve start at the origin
No particles have zero energy
The pressure of the original sample of gas is doubled at temperature T, state the effect of this change on the value of Y
No change
Identify a catalyst and name the organic product of the reaction
Fermentation of an aqueous solution of glucose
C- yeast
O- ethanol
Identify a catalyst and name the organic product of the reaction
Hydration of but-2-ene
H3PO4 / H2SO4
Butan -2-ol
Suggest why a small increase in temperature can lead to a large increase in the reaction rate between colliding particles
More particles have the minimum amount of energy
Give the meaning of the term catalyst
Speeds up reaction rate without being chemically changed
State how the rate of the forward reaction and the rate of the reserve reaction are related to each other at equilibrium
In equilibrium forwards reaction = reversible reaction are reacting at the same rate
Give the meaning of the term dynamic in the context of dynamic equilibrium
Forward and backwards reactions happen at the same rate
A + B ↔️ C + D
The total pressure on the system is increased at constant temperature. State and explain the effect of this change ( if any)
No change
Equal amount of moles of each
A + B ↔️ C + D
State and explain the effect of this change on the time taken to reach this equlibrium
Rate of reaction is quicker
Less frequent collision because there is more space
By referring to electrons, explain the meaning of the term oxidising agent
Accepts electrons
Explain the meaning of oxidation state
Oxidation state its the charge of the element in a compound
Write a half-equation for the oxidation of copper to copper(II) ions
Cu ➡️ Cu2+ + 2e-
X + 2Y ↔️ Z
The student added a few drops of Y to the equlibrium mixture of X, Y and Z
Suggest how the colour of the mixture changed. Give a reason for your answer
Colour change - no change
Went more orange
Equilibrium shifted to the right
To oppose the increase in the concentration of Y
X + 2Y ↔️ Z. 🔺H = -20
The student warmed the mixture. Predict the colour change when the equilibrium was warmed
Orange colour would fade
Gaseous ethanol can be used to convert hot copper (II) oxide into copper.
Deduce the role of ethanol in this reaction
Reduce the copper oxide
Chlorine and bromine are both oxidising agents
What is an oxidising agent
Gained electrons
Deduce a half-equation for the reduction of bromine in aqueous solution
Br2 + 2e- ➡️ 2Br-
Give a reason why chlorine is not formed when solid potassium chloride reacts with concentrated sulphuric acid
Chloride ions cant reduce sulphuric acid
Solid potassium bromide undergoes a redox reaction with concentrated sulphuric acid
Give the oxidation product formed potassium bromide
Bromine
Solid potassium bromide undergoes a redox reaction with concentrated sulphuric acid
Give the reduction product formed with sulphuric acid
Sulphur dioxide
State and explain the effect of an increase in pressure on the yield of nitrogen monoxide in the equilibrium
Wouldn’t effect equilibrium
Equal amount of moles on each side
Therefore Equilibrium wouldn’t move
State and explain the effect of an increase in temperature on the yield of nitrogen monoxide in the equilibrium
Increase
Forward reaction is endothermic
Endothermic reaction is favoured
explain why certain elements in periodic table are classified as p-block elements
elements in the p-block have their outer electron in p-orbital
explain the meaning of periodicity as applied to the properties of rows of elements in the periodic table. describe and explain the trends in atomic radius, in electronegativity and in conductivity for the elements sodium to argon
pattern in the change in the properties of a row of elements
repeated in the next row
atomic radius decrease across a row
number of protons increases
more attraction for electron in the same shell
electronegativity increases across a row
number of protons increase
atomic radius decreases (more attraction for bonding/ shared electrons)
conductivity decreases across a row (significant drop from Al to Si)
Na-Al are metals
Si-Ar non metals (molecular/covalent)
electrons are free to move
indenify the period 2 element (from carbon to fluorine) that has the largest atomic radius.
explain your answer
carbon
least amount of protons
same shielding
state the general trend in first ionisation energies from carbon to neon. deduce the element that deviates from this trend and explain why this element deviates from the trend
trend = increase
element that deviates = oxygen
outer orbital has 4 electrons, the one you want to remove has two electrons in the orbital so the extra electron provides extra repulsion
write an equation (including state symbols) for the reaction than the first ionisation energy of carbon is measured
C (g) —– C+(g) + e-
explain why the second ionisation energy of carbon is higher that the first ionisation energy are carbon
second electron is near to the nucleus
deduce the element in period 2 from lithium to neon that has the highest second ionisation energy
lithium
write an equation (including state symbols) to show the reaction that occurs when the second ionisation energy of magnesium
Mg+(g) —- Mg2+(g) +e-
explain why the second ionisation energy of magnesium is greater than the first ionisation energy of magnesium
closer to the nucleus so its harder to remove an electron
state and explain the general trend in the first ionisation energies of period 3 elements sodium to chlorine
trend = increase
more protons
electron is taken from the same shell
state how the element sulphur deviates from the general trend in first ionisation energies across period 3 explain your answer
ionisation energy is lower than phosphorus
extra electrons repel each other
state the typeof structure shown by the crystal of scallion. explain why the melting point of scallion is very high
giant covalent structure
covalently bonded which are strong
lots of energy is needed to break the bonds
state the type of structure shown by crystals of sulphur and phosphorus. explain why the melting point of sulphur is higher than the melting point of phosphorus
macular bonding S8 and P4
more van Der walls to break
P is smaller than s
explain why aluminium is malleable
layers can slide over each other
explain why the melting point of aluminium is higher than the melting point of sodium
aluminium bigger charge
more delocalised electrons
stronger metallic bonds
state the trend in atomic radius from phosphorus to chlorine and explain the trend
decrease in trend
more protons across a period
outer electrons are added to the same shell
an electron is added each time
in terms of atomic structure, explain why van Der walls forces in liquid argon are very weak
single atom with electrons close to the atoms
can not be easily polarised
which of these elements has the highest second ionisation energy? Na Mg Ne Ar
Na
more attraction
explain why the atomic radii of the elements decrease across period3 from sodium to chlorine
more protons
attraction between the nucleus and electrons
explain why the melting point of sulfur is greater that that of phosphorus
sulfur is bigger
more van der Waals forces
explain in terms of structure and bonding why the melting point is carbon is high
ginat covalent structure (marcocular)
4 carbon bonded
strong covalent bonds
state the meaning of the term electronegativity
ability to attract a pair of covalent bonded electrons
satte and explain the trend in electronegativity values across period 3 from sodium to chlorine
increase
more protons added
in the same shell
why is meant by first ionisation energy?
energy needed to from an electron from 1 mole of gaseous element to from gaseous +1 ion
what is maximum number of electrons that ca be accommodates in an s sub-shell
2
state a medical use of barium sulphate and state why the use of bariums sulphate is safe
coat intestine so they show up on a x-ray
insoluble
magnesium hydroxide is used in antacid preparations to neutralise excess stomach acid
write an equation
Mg(OH)2 + 2HCl —- MgCl2 + 2H2O
solutions of. aroma hydroxide are used in the titration of weak acids. state why magnesium hydroxide solution could not be used for this purpose
not soluble
magnesium burns with bright white light and is used in flares and fireworks. use your knowledge of the reactions of group 2 metals with water to explain why water should not be used to put out a fire in which magnesium metal is burning
would make magnesium hydroxide and hydrogen
hydrogen would explode
a student investigated how the initial rate of reaction between sulphuric acid and magnesium at 20C is affected by the concentration of acid
H2SO4 + Mg —— MgSO4 + H2
the student mage measurements every 2o seconds for 5 minutes
- state a measurement that the student show make every 20 seconds.
volume of gas (hydrogen ) realised
gas syringe
a student investigated how the initial rate of reaction between sulphuric acid and magnesium at 20C is affected by the concentration of acid
H2SO4 + Mg —— MgSO4 + H2
the student mage measurements every 2o seconds for 5 minutes
state on condition other than temperature and pressure that would need yo be kept constant
same mass as magnesium
suggest one method the student could use for removing soluble impurities from the sample of magnesium hydroxide that has been separated
wash with water
solubility in water Mg(OH)2 to Ba(OH)2
- decrease
- increase
- stays the same
increase
first ionisation energy Mg to Ba
- decrease
- increase
- stays the same
decrease
atomic radius
- decrease
- increase
- stays the same
increases
explain why calcium has a higher melting point than strontium
delocalised electrons closer to the nucleus
acidified barium chloride solution is used as reagent to test for sulphate ions. state why sulphuric acid should not be used to acidify the barium chloride?
sulphuric acid would make a white precipitate
write an equation for the reaction between strontium chloride solution and sodium sulphate solution
SrCl2 (aq) + Na2SO4(aq) —- SrSO4 (s) + 2NaCl(aq)
describe briefly how you could obtain strontium sulphate from a mixture of strontium carbonate and strontium sulphate
add nitric acid
filter out strontium sulphate
medicines for the treatment of nervous disorders contain calcium bromide. silver bitrate, acidified with dilute nitric acid, can be used together with another reagent to test for the presence of bromide ions in a solution of a medicine
describe brief how you would carry out this test and state what you would observe
the mixture would go clear to cream and then you would add excess dilute ammonia and then there would be no change
explain why calcium has a higher melting point that strontium
sea of delocalised electrons are closer to the positive nucleus to the attraction is more so more energy is needed to break the bonds (stronger attraction)
write an equation for the reaction of magnesium with oxygen
write an equation for the reaction of magnesium with cold water
give a medical use for the magnesium compound formed in the reaction of magnesium with cold water
2Mg(s) + O2(g) —- 2MgO(aq)
Mg(s) + 2H2O(l) ——Mg(OH)2 (aq) + H2(g)
neutralise stomach acid
give one reason why silver nitrate solution was acidified before it was used in this test
react with ions that would interfere
prevent the form of other silver prepitate
method that the scientists used could not detect one type of halide ion.
fluorine
froms a clear precipitate so you couldnt see it
state and explain the trend in electronegativity down group 7 from fluorine to iodine
decrease
attraction between the nucleus and electrons increase distance
increased shielding
describe and explain the trend in the boiling points of the elements down group 7 from fluorine and iodine
boiling point increase
atoms get bigger
forces are stronger so more energy is needed
sodium bromide reacts with concentrated sulphuric acid in a different way from sodium chloride
write an equation for this reaction of sodium bromide and explain why bromide ions react differently from chloride ions
2NaBr + 2H2SO4 —– Na2SO4 + 2H2O + Br2 + SO2
Bromine is bigger
better reducing agent
a colourless solution contains a mixture of sodium chloride ad sodium bromide
using aqueous nitrate and any other regents of your choice, develop a procedure a pure sample of silver bromide from this mixture. explain each step in the procedure and illustrate your explanations with equations
add silver nitrate
Ag+ + Br- —— AgBr (cream)
Ag+ + Cl ——- AgCl (yellow)
add dilute ammonia
give one observation that you would make when this reaction occurs
red liquid
explain why chlorine has a lower boiling point than bromide
smaller molecules
van der Waals forces are weaker
which one of the following solutions would not give a white precipitate when added to barium chloride
- silver nitrate solution
- dilute sulphuric acid
- sodium sulphate solution
- sodium nitrate solution
sodium nitrate solution
an aqueous solution of sodium salt gave no precipitate when treated with either silver nitrate solution or barium chloride solution. which one of the following could be the formula of the sodium salt?
- NaI
- Na2SO4
- NaBr
- NaF
NaF
which one of the following statement is true?
- bromine liberates iodine from aqueous sodium iodide
- chlorine liberates Florine from aqueous sodium fluoride
- silver iodide is soluble in aqueous ammonia
- concentrated sulphuric acid liberates chlorine from solid sodium chloride
chlorine liberates Florine from aqueous sodium fluoride
which substance is not produced in a redox reaction when slid sodium iodide reactants with concentrated sulphuric acid H2S HI SO2 I2
HI
which of these substances reacts most rapidly to produce a silver halide precipitate with acidify silver nitrate CH3Br CH3Cl CH3F CH3I
CH3F
Explain what is meant by the term hydrcarbon
A compound that only contains hydrogen and carbon
Explain what is meant by the term fuel
Substance that produces heat energy when they are burnt
Write an equation for the incomplete combustion of butane to produce carbon monoxide and water
C4H10 + 9/2O2 —— 4CO + 5H2O
Under what condition would you expect incomplete combustion occur
Limited supply of oxygen
Ethane can be cracked in the presence of catalyst to produce ethene and hydrogen
Write an equation for this reaction
C2H6 ——- C2H4 + H2
Ethane can be cracked in the presence of catalyst to produce ethene and hydrogen
Suitable catalyst
Zeolite
State one reason by cracking is important
Makes smaller hydrogen hydrogen carbon which are more in demand
State one essential condition for the formation of NO in an engine. Write an equation for the reaction in which NO if formed
Condition - extreme temperature / or a spark
Equation - N2 + O2 —– 2NO
All new petrol-engine cars must be fitted with a catalytic converter. Name one of the metals used as a catalyst in a catalytic converter
Platinum
Write an equation to show CO and NO react with each other in a catalytic converter
2CO + 2NO —– N2 + 2CO2
State why sulphur dioxide gas is sometimes found in the exhaust gases if petrol-engined cars. Give one adverse effect of sulphur dioxide on the environment
SO2 —- contained within fuels
Causes acid rain
Give the name of substance from which paraffin is obtained. State the name of the process
Crude oil
Fractional distillation
Oxides of nitrogen are also produced during the combustion of paraffin in air. Explain how these oxides of nitrogen are formed
When there is a spark and a high temperature nitrogen and oxygen in the air bond to make nitrogen oxide
Write an equation to show how nitrogen monoxide in the air is converted into nitrogen oxide
2NO + O2 —– 2NO2
Explain why the melting point of dodecane is higher than the melting point of the straight-chain alkane produced by cracking dodecane
Dodecane has a high melting point because it has stronger van der wall forces.
Longer chain
In some refrigeration systems CHF3 has replaced CClF3 because of concerns about ozone depletion
Identify the species formed from CClF3 that is responsible for the catalytic decomposition of ozone in the upper atmosphere
Chloride
identify the characteristic of the halogenalkane molecule that enables it to undergo this type of reaction
polar bonds
state what is meant by the term nucleophile
electron pair donator
explain why an excess of ammonia is needed in this reaction
CH3CH2Br + NH3 ——- CH3CH2NH2
to increase the forwards reaction
state the meaning of the term structural isomers
same molecular formula but different structure
identify the condition that cause a bond in CCl4 to break in the upper atmosphere. deduce an equation for the formation of the reactive species
condition - UV light
Equation -
CCl4 —- CCl3; + Cl;
one of the reactive species formed from CCl4 acts a catalyst in the decomposition of the ozone
(write two equations)
equation 1
Cl; +O3 —- O2 + ClO;
equation 2
ClO + O3 —– Cl; + 2O2
state the meaning of the term hydrolysis
breaking bonds using water
state the colour of the precipitate formed when iodide ions react with silver nitrate and give an equation
yellow
I- + Ag+ —– AgI
use your knowledge of the reactions of halide ions with silver nitrate to suggest why the student did not include 1-florobutane in this experiment
AgF is dissolved
so there is not result
state the meaning of the term nucleophile
electron pair donator
why are fluoroalkanes unreactive ? a Florine is highly electronegative b F- ion is very stable c polar molecules d C-F bond is very strong
d
C-F bond is very strong
explain the meaning of nucleophile
electron pair donator
Explain the meaning of substitution
halogen is substuiter for the nucleophile
explain the meaning of hydrolysis
splitting molecules using water
explain the meaning of bond enthalpy
amount of energy needed to break a bond
chloromethane can be made by the reaction of chlorine and methane
give one essential conditions fro this reaction
UV light
chloromethane can be made by the reaction of chlorine and methane
name the mechanism
free radical substitution
chloromethane can be made by the reaction of chlorine and methane
further substation can occur during this reaction. identify the main organic product when a large excess of chlorine is used in this reaction
CCl4
ethanenitrile can be made by reacting chloromethane with potassium cyanide
write an equation
CH3Cl + KCN ——- KCl- + CH3CN
ethanenitrile can be made by reacting chloromethane with potassium cyanide
name the mechanism
nucleophilic substitution
ethanenitrile can be hydrolysed to a carboxylic acid by heating it under reflux with a dilute acid. identify the carboxylic acid formed in this reaction
ethanic acid
chloromethane can react with ammonia to produce a primary amine.
what feature of the chloromethane molecule makes it susceptible to attack by an ammonia molecules?
polar bonds
name the amine produce in this reaction
methylamine
which statement about ethene is correct?
A. no geometric isomers because there is free rotation around the C=C bond
B. reacts with Her in a nucleophilic addition reaction
C. burns in excess oxygen to produce carbon dioxide and water
D. C=C bon is twice as strong as the C-C bond
C
burns in excess oxygen to produce carbon dioxide and water
it is possible to convert but-1-ene into its structural isomer but-2-ene
what is the type of isomerism ?
positional isomer
explain the meaning of the term electrophile
electron pair acceptor
explain the meaning of the term addition
double goes a single bond
explain why bromine, a non-polar molecule, is able to react with propene?
bromine get close to the double bond (electron rich) the negativity cause the electrons to repel which causes a dipole
the polymerisation of propene to form poly(propene) is an important industrial process
name the process
additional polymerisation
in a trial experiment, the student failed to fill the burette correctly so that the gap between the tap and the tip of the burette still contained air.
suggest what effect this would have on the measured volume of bromine water in the trail. explain why?
more have been used then measured
the level on the burette would go down before any liquid is realsed
other than incorrect use of the burette, suggest a reason for the inconsistency in the students results
drops of oil coulee be different sizes
outline how the student could improve this practical procedure to determine the number of C=C double bonds in a molcule of the oil so that more consistent results are obtained
use more drops of oil
mix/ stir so that the oil can dissolve
make it up to 250ml
titrate
state the meaning of the term molecular ion
an molecule that has been ionised but not broken up
state the meaning of catalyst
speeds up the reaction but isn’t used up
state the meaning of the term hydration
adding water
suggest how the chemist could obtain a sample of the compound for analysis from the mixture of volatile liquid
GLC
suggest why there is two molecular ion peaks
two isotopes
explain how infrared spectrometry can be used to show that an aldehyde is definitely pentanal
peak in the 1680-1750
fingerprint region
give one reason why 2,3,3,3-tetrafluoropropene is more environmentally acceptable refrigerant than chlorodifluoromethane
no chlorine
state the purpose of the anti-bumping granules
prevent to much vigour boiling
identify the feature of the double bond in (E)-pent-3-en-2-ol and that in (Z)-pent-3-en-2-ol that causes these two compounds to be stereoisomer
restricted rotation
state the meaning of carbon-neutral
it takes in the same amount of CO2 as it realises
give one disadvantage of the use of crops for the production of ethanol
slow process
suggest one advantage and one disadvantage for industry of carrying out the termination at this high temperature
ad- process quicker
dis- uses more energy
