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Chemistry > Exam questions > Flashcards

Exam questions Flashcards

1
Q

two characteristics of a homologous series (2)

A
  • general formula

- similar chemical properties

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2
Q

suggest why the branched chain isomer shown above has a lower boiling point? (2)

A
  • less surface area

- weaker van der waals

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3
Q

state what is meant by the term stereoisomers (2)

A
  • same structural formula

- different orentation

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4
Q

explain how these oxides of nitrogen are formed (2)

A

when there is a spark and a high-temperature nitrogen and oxygen in the air bond together

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5
Q

Nucleophile (1)

A

electron pair donator

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6
Q

substitution, as applied to nucleophilic substitution in a haloalkane (1)

A

halogen is substituted

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7
Q

hydrolysis (1)

A

splitting molecules using water

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8
Q

describe how ions are formed in a time of flight mass spectrometer (2)

A
  • high voltage is applied to the sample
  • element vapourised into gas
  • electron knock out or orbit
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9
Q

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)

A
  • ions are accelerated by an electric field

- only ions will create a current when they hit the plate

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10
Q

outline how the mass spectrometer is able to separate two species to give two peaks (4)

A
  • positive ion accelerates by an electric field
  • to a constant kinetic energy
  • lighter ions travel quicker
  • so will be detected first
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11
Q

why is the first ionisation energy of Krypton is greater than that of bromine (1)

A

more protons than bromine

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12
Q

in 1963, Krypton was found to react with fluorine. state why this discovery was unexpected

A

krypton is a noble gas

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13
Q

Describe how ions are formed in time of flight mass spectrometer

A

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

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14
Q

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

A

Ions are accelerated by an electric field

Only ions will create a current when they hit the plate

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15
Q

Outline how the TOF mass spectrometer is able to separate two species to give two peaks

A

Positive ion accelerate by an electric field
To constant kinetic energy
Lighter ion travels quicker
So will be detected first

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16
Q

Define the term relative atomic mass

A

Average mass of one atom / (1/12) of a carbon 12 atom

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17
Q

State why the isotope 10B and 11B have similar chemical reactions

A

Same number of electrons

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18
Q

Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron

A

You have to remove an electron from a positive ion which requires more energy

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19
Q

Give one reason why the second ionisation energy of silicon is lower than the second ionisation energy of aluminium

A

You have to remove an electron from a shell (3p orbital) needs more energy shell than the ‘s’ shell

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20
Q

State the type of reaction that occurs when calcium carbonate reacts with nitric acid

A

Neutralisation

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21
Q

Explain why the melting point of sodium chloride is high

A

Strong electrostatic attraction between the positive and negative ions, you need a lot of heat to overcome the forces

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22
Q

Name the type of bonding in sodium chloride

A

Ionic

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23
Q

Suggest why the melting point if sodium iodide is lower than the melting point of sodium bromide

A

Iodide is lower on the periodic table than sodium so its less reactive

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24
Q

What is the formula of calcium nitrate (IV)

A CaNO3
B Ca(NO3)2
C Ca2NO2
D Ca(NO2)2

A

B

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25
Q

State the meaning of the term covalent bond

A

Chemical bond where a pair of electrons are shared between two atoms

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26
Q

BF4-

Name the type of bond formed when a molecule of BF3 reacts with an F- ion. Explain how the bond is formed

A

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

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27
Q

Explain why nickel has a high melting point

A

They are strong because a lot of force has to be used to overcome the force of attraction between electron and positive ions

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28
Q

Explain why nickel is ductile

A

Its layers can side over each other

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29
Q

Define the term electronegativity

A

The power of the atom to attract an electron in a covalent bond

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30
Q

Explain how the strongest type of intermolecular force in liquid HF arises

A

Large difference in electronegativity between H and F and there is a dipole formed which are then attracted into each other

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31
Q

Explain the trend in the boiling points of hydrogen halides from HCl and HI

A

Van der waals

Increasing size

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32
Q

Give one reason why the boiling point of HF is higher than that of all the other hydrogen halides

A

Hydrogen bonding needs more energy to break the bonds

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33
Q

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

A

Iodine
Covalent bonds
Molecular
Weak van der waals forces

Diamond
Giant molecular
Covalent bonds
Higher melting point

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34
Q

Predict the shape of the AlH4-

Explain why it has this shape

A

Tetrahedral

Equal repulsion form four bonding pairs

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35
Q

Outline how the mass spectrometer is able to separate these two species to give two peaks

A

The ion is accelerated by the electric field to a constant kinetic energy. One species would be lighter so would be detected first

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36
Q

Explain in the terms of electronegativity why the boiling point of H2S2 is lower than H2O2

A

Oxygen has a higher electronegativity change than sulphur

No hydrogen bonding

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37
Q

Describe the structure of and bonding in graphite and explain why the melting point of graphite is very high

A

Covalent bonds need a lot of energy to break
Graphite has layers
Have to break lots of bonds

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38
Q

Explain why iodine vaporises when heated gently

A

Weak intermolecular forces (weak van der waals) so not much energy is needed to break the bonds

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39
Q

State why iodine is a very poor conductor of electricity

A

No delocalised electrons

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40
Q

State two characteristics of a homologous series

A

General formula

Similar chemical properties

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41
Q

Suggest why the branched chain isomer shown above has a lower boiling point than octane

A

Less surface area

Van der waals

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42
Q

State what is meant by the term stereoisomers

A

Same structural formula

Different orientation

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43
Q

Suggest one improvement that would reduce errors due to heat loss in the student experiment ( p= mcΔt )

A

If you put a lid on the breaker so no gas can escape or heat

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44
Q

Give the meaning of the term mean bond enthalpy

A

Change in heat breaking the covalent bond

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45
Q

Give one reason why titanium is not extracted from titanium oxide using carbon

A

Product is brittle

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46
Q

Give the meaning of the term enthalpy change

A

Heat given out or taken in when bonds are broken at constant pressure

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47
Q

State hess’s law

A

Heat change at constant pressure

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48
Q

Define the term standard enthalpy of formation

A

When one mole of substance is bonded to form its elements with all reactants and products in their standard states

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49
Q

Explain the term mean bond enthalpy

A

The average bond enthalpy produced from different bonds ( enthalpy energy to break a covalent bond)

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50
Q

Define the term atomic number

A

Amount of protons in the nucleus

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51
Q

Explain why atoms of an element may have different mass number

A

Different number of neutrons

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52
Q

The first ionisation energy of krypton is greater than that of bromine

A

More protons than bromine

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53
Q

State and explain the trend in electronegativity values across period 3 from sodium to chlorine

A

It would increase

Number of protons increase in the same shell

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54
Q

Predict the type of crystal structure in solid zinc fluoride and explain why its melting point is high

A

Ionic
Strong electrostatic forces between ions so a lot of energy is needed to over come the electrostatic force between oppositely charged ions

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55
Q

Name the device used to ionise atoms in a mass spectrometer

A

Electron gun

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56
Q

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

A

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

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57
Q

state the strongest type of intermolecular force between hydrogen fluorine molecules

A

hydrogen bonding

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58
Q

the boiling points of fluorine and hydrogen Florine are low. explain why?

A

fluorine is covalently bonded together by weak van Waals forces where the hydrogen bonds are stronger than van waals

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59
Q

identify from the period 2 elements that has the largest atomic radius

A

lithium

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60
Q

state the general trend in first ionisation energies for the period 2 elements lithium to nitrogen

A

increases

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61
Q

identify the element that deviates from this general trend, from lithium to nitrogen, and explain your answer

A

Boron

electron removed from the 2p orbital which is higher in energy

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62
Q

explain in terms of structure and bonding why the melting point of carbon is high

A

giant molecular
strong covalent bonds
bonds must be broken

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63
Q

name a raw material from which hexane is obtained

A

crude oil

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64
Q

name the process used to obtain hexane from this raw material

A

fractional distillation

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65
Q

state the type of cracking that produces a high percentage of alkenes. state the conditions needed for this type of cracking

A

termal cracking

high temperature and high pressure

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66
Q

explain the main economic reason why alkanes are cracked

A

short-chain alkanes are more in demand so are worth more money than long-chained alkanes

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67
Q

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

A

platinum

bigger surface area

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68
Q

suggest one reason why the yield of nitrogen dioxide formed during this reaction is often less than expected

A

decomposition not complete

by-products formed

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69
Q

suggest one reason why it is difficult to obtain a pure sample of nitrogen dioxide from this reaction

A

hard to separate the two gases

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70
Q

state the type of structural isomerism shown by but-1-ene and but-2-ene

A

positional

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71
Q

in industry, this fermentation reaction is carried out at 35 rather than 25. suggest a advantage and disadvantage

A 
Ad= reaction would happen quicker
Dis= uses more energy
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72
Q

state a condition of thermal cracking

A

high pressure and high temperature

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73
Q

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

A

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
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74
Q

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

A
  • measured volume would be greater

- level in burette falls as the tap is filled before any liquid is delieved

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75
Q

other an not filling the bottom of the tap, suggest a reason for an inconsistency in the students results

A

drop size may vary

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76
Q

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

A
  • larger single volume of oil
  • dissolve oil
  • transfer to conceal flask and make up 250cm3
  • tritate (25cm3) sample from the flask
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77
Q

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

A

C

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78
Q

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

A

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79
Q 
which of these substances does not contribute to the greenhouse effect?
A-unburned hydrocarbons
B-carbon dioxide
C-water vapour
D-nitrogen
A

D

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80
Q

suggest a name for this type of reaction that iron(III) nitrate undergoes

A

thermal decomposition

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81
Q

suggest why the iron (III) oxide obtained is pure

A

other products are gases

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82
Q

explain, in terms of its structure and bonding, why nickel has a high melting point

A

nickel has a high melting point because its metallic bonded where there is a sea of delocalised electrons around the positive ions

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83
Q

explain why nickel is ductile

A

layers that can slide over each other

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84
Q

name the strongest attractive force between two ammonia molecules

A

hydrogen bonding

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85
Q

give the meaning of the term electronegativity

A

ability of an molecules to attract on electron pair in a covalent bond

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86
Q

oxides of nitrogen are also produced during the combustion of paraffin in air. explain how these oxides of nitrogen are formed

A

a spark in engine creates a high temperature where nitrogen an oxygen in the air

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87
Q

explain why the melting point of Dodecanese is higher than the melting point of the straight-chain alkane produced by cracking dodecane

A

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

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88
Q

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

A

ionic bonding
oppositely charged ions
strong attraction between ions

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89
Q

suggest one reason other than incomplete combustion or heat transfer to the atmosphere why the students value of enthalpy is different

A

heating in the container

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90
Q

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

A

heat loss is a bigger uncertainty

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91
Q

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

A

distillation
heat the mixture up
distilled off then condensed

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92
Q

explain how a catalyst works

A

provides an alternate route with a lower activation energy

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93
Q

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

A 
large surface area
reduces cost (uses less money)
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94
Q

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

A

bromine solution

orange to colourless

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95
Q

explain why 1,1,1-trifluoroethane does not lead to the depletion of the ozone in the upper atmosphere

A

C-F bond is strong

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96
Q

anti-bumping granules are placed in the flask when refluxing. suggest why these granules bumping

A

preventing vicious boiling

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97
Q

Magnesism oxide is a white solid with a higher melting point

Explain how the ions are held together in solid magnesium oxide

A

Electrons are transferred

Electrostatic attraction between charged ions

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98
Q

Addition polymerisation

A

Small unsaturated monors joined up by the opening of the double bond allowing them to join up to form a long carbon chain

99
Q

What is meant by polymerisation

A

A chemical process that combines several monomers to form a polymer

100
Q

Solvent molecules evaporate easily

Explain why substances made of simple molecules evaporate easily

A

They have weak forces between the molecules so they can be broken eaisly by putting only a small amount of energy put in

101
Q

How does the number of atoms in one mole of argon compare with the number of molecules in one mole of ammonia?

A

Same

one mole of anything in the same

102
Q

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

A

Measure the amount of gas given off at regular time intervals

103
Q

Na2S2O3 + 2HCl ➡️ 2NaCl + S + SO2 +H2O

Identify the insoluble product of the reaction which forms the precipitate

A

Sulfur

104
Q

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

A

The minimum amount of energy needed for successful collisions

105
Q

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

A

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

106
Q

What is meant by the term rate of reaction

A

Change in concentration in unit time

107
Q

On an maxwell Boltzmann graph

Why does the curve start at the origin

A

No particles have zero energy

108
Q

The pressure of the original sample of gas is doubled at temperature T, state the effect of this change on the value of Y

A

No change

109
Q

Identify a catalyst and name the organic product of the reaction

Fermentation of an aqueous solution of glucose

A

C- yeast

O- ethanol

110
Q

Identify a catalyst and name the organic product of the reaction

Hydration of but-2-ene

A

H3PO4 / H2SO4

Butan -2-ol

111
Q

Suggest why a small increase in temperature can lead to a large increase in the reaction rate between colliding particles

A

More particles have the minimum amount of energy

112
Q

Give the meaning of the term catalyst

A

Speeds up reaction rate without being chemically changed

113
Q

State how the rate of the forward reaction and the rate of the reserve reaction are related to each other at equilibrium

A

In equilibrium forwards reaction = reversible reaction are reacting at the same rate

114
Q

Give the meaning of the term dynamic in the context of dynamic equilibrium

A

Forward and backwards reactions happen at the same rate

115
Q

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)

A

No change

Equal amount of moles of each

116
Q

A + B ↔️ C + D

State and explain the effect of this change on the time taken to reach this equlibrium

A

Rate of reaction is quicker

Less frequent collision because there is more space

117
Q

By referring to electrons, explain the meaning of the term oxidising agent

A

Accepts electrons

118
Q

Explain the meaning of oxidation state

A

Oxidation state its the charge of the element in a compound

119
Q

Write a half-equation for the oxidation of copper to copper(II) ions

A

Cu ➡️ Cu2+ + 2e-

120
Q

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

A

Colour change - no change
Went more orange
Equilibrium shifted to the right
To oppose the increase in the concentration of Y

121
Q

X + 2Y ↔️ Z. 🔺H = -20

The student warmed the mixture. Predict the colour change when the equilibrium was warmed

A

Orange colour would fade

122
Q

Gaseous ethanol can be used to convert hot copper (II) oxide into copper.
Deduce the role of ethanol in this reaction

A

Reduce the copper oxide

123
Q

Chlorine and bromine are both oxidising agents

What is an oxidising agent

A

Gained electrons

124
Q

Deduce a half-equation for the reduction of bromine in aqueous solution

A

Br2 + 2e- ➡️ 2Br-

125
Q

Give a reason why chlorine is not formed when solid potassium chloride reacts with concentrated sulphuric acid

A

Chloride ions cant reduce sulphuric acid

126
Q

Solid potassium bromide undergoes a redox reaction with concentrated sulphuric acid

Give the oxidation product formed potassium bromide

A

Bromine

127
Q

Solid potassium bromide undergoes a redox reaction with concentrated sulphuric acid

Give the reduction product formed with sulphuric acid

A

Sulphur dioxide

128
Q

State and explain the effect of an increase in pressure on the yield of nitrogen monoxide in the equilibrium

A

Wouldn’t effect equilibrium
Equal amount of moles on each side
Therefore Equilibrium wouldn’t move

129
Q

State and explain the effect of an increase in temperature on the yield of nitrogen monoxide in the equilibrium

A

Increase
Forward reaction is endothermic
Endothermic reaction is favoured

130
Q

explain why certain elements in periodic table are classified as p-block elements

A

elements in the p-block have their outer electron in p-orbital

131
Q

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

A

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

132
Q

indenify the period 2 element (from carbon to fluorine) that has the largest atomic radius.
explain your answer

A

carbon
least amount of protons
same shielding

133
Q

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

A

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

134
Q

write an equation (including state symbols) for the reaction than the first ionisation energy of carbon is measured

A

C (g) —– C+(g) + e-

135
Q

explain why the second ionisation energy of carbon is higher that the first ionisation energy are carbon

A

second electron is near to the nucleus

136
Q

deduce the element in period 2 from lithium to neon that has the highest second ionisation energy

A

lithium

137
Q

write an equation (including state symbols) to show the reaction that occurs when the second ionisation energy of magnesium

A

Mg+(g) —- Mg2+(g) +e-

138
Q

explain why the second ionisation energy of magnesium is greater than the first ionisation energy of magnesium

A

closer to the nucleus so its harder to remove an electron

139
Q

state and explain the general trend in the first ionisation energies of period 3 elements sodium to chlorine

A

trend = increase
more protons
electron is taken from the same shell

140
Q

state how the element sulphur deviates from the general trend in first ionisation energies across period 3 explain your answer

A

ionisation energy is lower than phosphorus

extra electrons repel each other

141
Q

state the typeof structure shown by the crystal of scallion. explain why the melting point of scallion is very high

A

giant covalent structure
covalently bonded which are strong
lots of energy is needed to break the bonds

142
Q

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

A

macular bonding S8 and P4
more van Der walls to break
P is smaller than s

143
Q

explain why aluminium is malleable

A

layers can slide over each other

144
Q

explain why the melting point of aluminium is higher than the melting point of sodium

A

aluminium bigger charge
more delocalised electrons
stronger metallic bonds

145
Q

state the trend in atomic radius from phosphorus to chlorine and explain the trend

A

decrease in trend
more protons across a period
outer electrons are added to the same shell
an electron is added each time

146
Q

in terms of atomic structure, explain why van Der walls forces in liquid argon are very weak

A

single atom with electrons close to the atoms

can not be easily polarised

147
Q 
which of these elements has the highest second ionisation energy?
Na
Mg
Ne
Ar
A

Na

more attraction

148
Q

explain why the atomic radii of the elements decrease across period3 from sodium to chlorine

A

more protons

attraction between the nucleus and electrons

149
Q

explain why the melting point of sulfur is greater that that of phosphorus

A

sulfur is bigger

more van der Waals forces

150
Q

explain in terms of structure and bonding why the melting point is carbon is high

A

ginat covalent structure (marcocular)
4 carbon bonded
strong covalent bonds

151
Q

state the meaning of the term electronegativity

A

ability to attract a pair of covalent bonded electrons

152
Q

satte and explain the trend in electronegativity values across period 3 from sodium to chlorine

A

increase
more protons added
in the same shell

153
Q

why is meant by first ionisation energy?

A

energy needed to from an electron from 1 mole of gaseous element to from gaseous +1 ion

154
Q

what is maximum number of electrons that ca be accommodates in an s sub-shell

A

2

155
Q

state a medical use of barium sulphate and state why the use of bariums sulphate is safe

A

coat intestine so they show up on a x-ray

insoluble

156
Q

magnesium hydroxide is used in antacid preparations to neutralise excess stomach acid
write an equation

A

Mg(OH)2 + 2HCl —- MgCl2 + 2H2O

157
Q

solutions of. aroma hydroxide are used in the titration of weak acids. state why magnesium hydroxide solution could not be used for this purpose

A

not soluble

158
Q

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

A

would make magnesium hydroxide and hydrogen

hydrogen would explode

159
Q

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.
A

volume of gas (hydrogen ) realised

gas syringe

160
Q

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

A

same mass as magnesium

161
Q

suggest one method the student could use for removing soluble impurities from the sample of magnesium hydroxide that has been separated

A

wash with water

162
Q

solubility in water Mg(OH)2 to Ba(OH)2

  • decrease
  • increase
  • stays the same
A

increase

163
Q

first ionisation energy Mg to Ba

  • decrease
  • increase
  • stays the same
A

decrease

164
Q

atomic radius

  • decrease
  • increase
  • stays the same
A

increases

165
Q

explain why calcium has a higher melting point than strontium

A

delocalised electrons closer to the nucleus

166
Q

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?

A

sulphuric acid would make a white precipitate

167
Q

write an equation for the reaction between strontium chloride solution and sodium sulphate solution

A

SrCl2 (aq) + Na2SO4(aq) —- SrSO4 (s) + 2NaCl(aq)

168
Q

describe briefly how you could obtain strontium sulphate from a mixture of strontium carbonate and strontium sulphate

A

add nitric acid

filter out strontium sulphate

169
Q

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

A

the mixture would go clear to cream and then you would add excess dilute ammonia and then there would be no change

170
Q

explain why calcium has a higher melting point that strontium

A

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)

171
Q

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

A

2Mg(s) + O2(g) —- 2MgO(aq)

Mg(s) + 2H2O(l) ——Mg(OH)2 (aq) + H2(g)

neutralise stomach acid

172
Q

give one reason why silver nitrate solution was acidified before it was used in this test

A

react with ions that would interfere

prevent the form of other silver prepitate

173
Q

method that the scientists used could not detect one type of halide ion.

A

fluorine

froms a clear precipitate so you couldnt see it

174
Q

state and explain the trend in electronegativity down group 7 from fluorine to iodine

A

decrease
attraction between the nucleus and electrons increase distance
increased shielding

175
Q

describe and explain the trend in the boiling points of the elements down group 7 from fluorine and iodine

A

boiling point increase
atoms get bigger
forces are stronger so more energy is needed

176
Q

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

A

2NaBr + 2H2SO4 —– Na2SO4 + 2H2O + Br2 + SO2

Bromine is bigger
better reducing agent

177
Q

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

A

add silver nitrate
Ag+ + Br- —— AgBr (cream)
Ag+ + Cl ——- AgCl (yellow)

add dilute ammonia

178
Q

give one observation that you would make when this reaction occurs

A

red liquid

179
Q

explain why chlorine has a lower boiling point than bromide

A

smaller molecules

van der Waals forces are weaker

180
Q

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
A

sodium nitrate solution

181
Q

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
A

NaF

182
Q

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
A

chlorine liberates Florine from aqueous sodium fluoride

183
Q 
which substance is not produced in a redox reaction when slid sodium iodide reactants with concentrated sulphuric acid
H2S
HI
SO2
I2
A

HI

184
Q 
which of these substances reacts most rapidly to produce a silver halide precipitate with acidify silver nitrate 
CH3Br
CH3Cl
CH3F
CH3I
A

CH3F

185
Q

Explain what is meant by the term hydrcarbon

A

A compound that only contains hydrogen and carbon

186
Q

Explain what is meant by the term fuel

A

Substance that produces heat energy when they are burnt

187
Q

Write an equation for the incomplete combustion of butane to produce carbon monoxide and water

A

C4H10 + 9/2O2 —— 4CO + 5H2O

188
Q

Under what condition would you expect incomplete combustion occur

A

Limited supply of oxygen

189
Q

Ethane can be cracked in the presence of catalyst to produce ethene and hydrogen

Write an equation for this reaction

A

C2H6 ——- C2H4 + H2

190
Q

Ethane can be cracked in the presence of catalyst to produce ethene and hydrogen

Suitable catalyst

A

Zeolite

191
Q

State one reason by cracking is important

A

Makes smaller hydrogen hydrogen carbon which are more in demand

192
Q

State one essential condition for the formation of NO in an engine. Write an equation for the reaction in which NO if formed

A

Condition - extreme temperature / or a spark

Equation - N2 + O2 —– 2NO

193
Q

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

A

Platinum

194
Q

Write an equation to show CO and NO react with each other in a catalytic converter

A

2CO + 2NO —– N2 + 2CO2

195
Q

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

A

SO2 —- contained within fuels

Causes acid rain

196
Q

Give the name of substance from which paraffin is obtained. State the name of the process

A

Crude oil

Fractional distillation

197
Q

Oxides of nitrogen are also produced during the combustion of paraffin in air. Explain how these oxides of nitrogen are formed

A

When there is a spark and a high temperature nitrogen and oxygen in the air bond to make nitrogen oxide

198
Q

Write an equation to show how nitrogen monoxide in the air is converted into nitrogen oxide

A

2NO + O2 —– 2NO2

199
Q

Explain why the melting point of dodecane is higher than the melting point of the straight-chain alkane produced by cracking dodecane

A

Dodecane has a high melting point because it has stronger van der wall forces.
Longer chain

200
Q

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

A

Chloride

201
Q

identify the characteristic of the halogenalkane molecule that enables it to undergo this type of reaction

A

polar bonds

202
Q

state what is meant by the term nucleophile

A

electron pair donator

203
Q

explain why an excess of ammonia is needed in this reaction

CH3CH2Br + NH3 ——- CH3CH2NH2

A

to increase the forwards reaction

204
Q

state the meaning of the term structural isomers

A

same molecular formula but different structure

205
Q

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

A

condition - UV light
Equation -
CCl4 —- CCl3; + Cl;

206
Q

one of the reactive species formed from CCl4 acts a catalyst in the decomposition of the ozone
(write two equations)

A

equation 1
Cl; +O3 —- O2 + ClO;

equation 2
ClO + O3 —– Cl; + 2O2

207
Q

state the meaning of the term hydrolysis

A

breaking bonds using water

208
Q

state the colour of the precipitate formed when iodide ions react with silver nitrate and give an equation

A

yellow

I- + Ag+ —– AgI

209
Q

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

A

AgF is dissolved

so there is not result

210
Q

state the meaning of the term nucleophile

A

electron pair donator

211
Q 
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
A

d

C-F bond is very strong

212
Q

explain the meaning of nucleophile

A

electron pair donator

213
Q

Explain the meaning of substitution

A

halogen is substuiter for the nucleophile

214
Q

explain the meaning of hydrolysis

A

splitting molecules using water

215
Q

explain the meaning of bond enthalpy

A

amount of energy needed to break a bond

216
Q

chloromethane can be made by the reaction of chlorine and methane
give one essential conditions fro this reaction

A

UV light

217
Q

chloromethane can be made by the reaction of chlorine and methane
name the mechanism

A

free radical substitution

218
Q

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

A

CCl4

219
Q

ethanenitrile can be made by reacting chloromethane with potassium cyanide
write an equation

A

CH3Cl + KCN ——- KCl- + CH3CN

220
Q

ethanenitrile can be made by reacting chloromethane with potassium cyanide
name the mechanism

A

nucleophilic substitution

221
Q

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

A

ethanic acid

222
Q

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?

A

polar bonds

223
Q

name the amine produce in this reaction

A

methylamine

224
Q

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

A

C

burns in excess oxygen to produce carbon dioxide and water

225
Q

it is possible to convert but-1-ene into its structural isomer but-2-ene
what is the type of isomerism ?

A

positional isomer

226
Q

explain the meaning of the term electrophile

A

electron pair acceptor

227
Q

explain the meaning of the term addition

A

double goes a single bond

228
Q

explain why bromine, a non-polar molecule, is able to react with propene?

A

bromine get close to the double bond (electron rich) the negativity cause the electrons to repel which causes a dipole

229
Q

the polymerisation of propene to form poly(propene) is an important industrial process
name the process

A

additional polymerisation

230
Q

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?

A

more have been used then measured

the level on the burette would go down before any liquid is realsed

231
Q

other than incorrect use of the burette, suggest a reason for the inconsistency in the students results

A

drops of oil coulee be different sizes

232
Q

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

A

use more drops of oil
mix/ stir so that the oil can dissolve
make it up to 250ml
titrate

233
Q

state the meaning of the term molecular ion

A

an molecule that has been ionised but not broken up

234
Q

state the meaning of catalyst

A

speeds up the reaction but isn’t used up

235
Q

state the meaning of the term hydration

A

adding water

236
Q

suggest how the chemist could obtain a sample of the compound for analysis from the mixture of volatile liquid

A

GLC

237
Q

suggest why there is two molecular ion peaks

A

two isotopes

238
Q

explain how infrared spectrometry can be used to show that an aldehyde is definitely pentanal

A

peak in the 1680-1750

fingerprint region

239
Q

give one reason why 2,3,3,3-tetrafluoropropene is more environmentally acceptable refrigerant than chlorodifluoromethane

A

no chlorine

240
Q

state the purpose of the anti-bumping granules

A

prevent to much vigour boiling

241
Q

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

A

restricted rotation

242
Q

state the meaning of carbon-neutral

A

it takes in the same amount of CO2 as it realises

243
Q

give one disadvantage of the use of crops for the production of ethanol

A

slow process

244
Q

suggest one advantage and one disadvantage for industry of carrying out the termination at this high temperature

A

ad- process quicker

dis- uses more energy

Chemistry (20 decks)

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