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IGCSE Edexcel Chemistry > Random Stuff Double > Flashcards

Random Stuff Double Flashcards

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1
Q

Chemical equation for decomposition of hydrogen peroxide

A

2H2O2 —> 2H2O + O2

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2
Q

Explain why water has much lower melting point than sodium oxide

A

Attractions between water molecules (covalent bonds) are much weaker so easily overcome with little energy. Whereas the attraction between sodium and oxide ions is a lot stronger as ionic bonds are stronger and need lots more energy for bonds to break.

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3
Q

The electronic configuration of a sodium atom is 2.8.1
Sodium oxide, Na2O, is an ionic compound formed when sodium reacts with oxygen.
Describe, in terms of electrons, what happens when sodium oxide is formed in this reaction

A

Electron transfer
Sodium loses, oxygen gains
Sodium loses 1 electron and oxygen needs to gain 2 electrons

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4
Q

define activation energy

A

minimum amout of energy reqiured by colliding particles to react

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5
Q

define isomerism

A

compounds with same molecular, different structural

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6
Q

4 characteristics of same homologous series

A
  1. trend in physical
  2. similar chemical
  3. same general formula
  4. each group differs by CH2
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7
Q

conditions for cracking

A

600-700 degrees
alumina or silica catalyst

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8
Q

define cracking

A

thermal decomposition method to convert longer chain molecules into shorter more useful short chain alkanes or alkenes to meet supply and demand

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9
Q

define ionic bonding

A

strong electrostatic force of attraction between oppositely charged ions

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10
Q

which bonding is shown through dot and cross diagrams

A

covalent, electrons need to add up to 8, can be from multiple of same elements to add up

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11
Q

order of crude oils from 40degrees to 400 degrees

A
  1. refinery gas
  2. gasoline
  3. kerosene
  4. diesel
  5. fuel oil
  6. bitumen
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12
Q

does refinery gas or bitumen have a high viscosity and high boiling point

A

bitumen

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13
Q

what happens as you go down from refinery gas to bitumen

A
  1. boiling point increase
  2. viscosity increases, darker colour
  3. longer molecules - higher boiling point to break
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14
Q

process used to separate crude oils

A

fractional distillation

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15
Q

explain why crude oil containing sulfur or oxides of nitrogen as an impurity is a problem when using crude oil fractions as fuels

A

**when sulfur is burned, it forms sulfur dioxide and it can mix with rain to form acid rain. **acid rain makes land infertile, corrodes limestone buildings and destroys wildlife and ecosystems.

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16
Q

Uses of :
Refinery gas
Gasoline
Kerosene
Diesel
Fuel Oil
Bitumen

A
  1. domestic heating and cooking
  2. fuel for cars
  3. fuel for domestic heating, fuel for aircraft
  4. fuel for buses and train engines, trucks
  5. fuel for ships and industrial heating
  6. used to pave roads
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17
Q

cations
ammonium
hydrogen
silver
lead
zinc

A
  1. NH4 +
  2. H +
  3. Ag +
  4. Pb 2+
  5. Zn 2+
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18
Q

anions
Hydroxide
Nitrate
carbonate
sulfate

A
  1. OH -
  2. No3 -
  3. CO3 2-
  4. SO4 2-
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19
Q

Does diamond conduct electricity

A

Giant Covalent Structure
* No charged species that are free to move
so the substance won’t conduct electricity

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20
Q

Does graphite conduct electricity

A

Giant Covalent
Electrons are present between the layers of carbon atoms (electricity is a flow of electrons) and these delocalised electrons can move and carry a current.
 Graphite will conduct electricity.

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21
Q

Does Fullerene C60 conduct electricity

A

Simple molecular Structure
* No charged species that are free to move so the substance won’t conduct electricity

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22
Q

Does diamond have a high boiling point?

A

Giant covalent structure.
* Many strong covalent bonds (Electrostatic force of attraction between the shared pair of electrons and the nuclei of the atoms involved).
* Each carbon atoms is bonded to 4 other carbon atoms (tetrahedral arrangement)
* These bonds require lots of energy to break.
* Therefore these substances have very high melting points.

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23
Q

Does graphite have a high boiling point?

A

Giant covalent structure.
* Many strong covalent bonds
* Each carbon atoms is bonded to 3 other carbon atoms. One electron from each atom is delocalised(not involved in bonding)- this leads to electrical conductivity (see below)
* These require lots of energy to break.
* Therefore these substances have very high melting points.

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24
Q

Does fullerene C60 have a high boiling point?

A

NO
(larger) simple molecular structure.
* Weak intermolecular forces of attraction between the molecules.
* These require little energy to overcome them (break)
* Therefore these substances have low melting points, but higher than other smaller molecules.
As the size of molecules increases, there are more/stronger intermolecular forces and the melting/boiling points increase.

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25
Q

State why diamond is hard, but graphite is soft

A

diamond –> tetrahedral structure, 3D structure with each carbon bonded to 4 other carbons, so fixed lattice position
graphite –> has layers that can slide over each other

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26
Q

Diffusion of ammonia and hydrogen chloride

What is the white ring of solid ?

A

ammonium chloride

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27
Q

explain why ammonium chloride forms closer to hydrogen chloride than ammonia solution

A

ammonia diffuses faster

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28
Q

white ring forms after 5 minutes, explain why it takes so long even though gas particles move very fast

A

air particles in tube, so gas particles hit air particles, so diffusion is slower

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29
Q

give chemical equation for complete combustion of pentane (should be fully balanced)

A

C5H12 + 8 O2 –> 5 CO2 + 6 H2O

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30
Q

why is carbon monoxide dangerous

A

reduces blood’s capacity to carry oxygen around body

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31
Q

describe how crude oil is separated into fractions

A
  1. crude oil is pre heated and vapourised
  2. vapour fed into fractionating column, hotter at bottom, cooler at top
  3. vapour rises, cools and condenses at different heights
  4. different fractions have different boiling point ranges
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32
Q

define molecule

A

fixed number of atoms joined together by covalent bonds

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33
Q

what is empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae

A

empirical = smallest ratio
molecular =number of stuff there
general = general formula for homologous series
displayed = how it is drawn
structural = how it is set out

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34
Q

how to work out empirical formulae

A

1.find mass
2. find Ar or Mr
3. find moles (moles = mass/Mr)
4. divide by smallest number, round number to nearest 1/2 number and then times by 2 if needed

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35
Q

define saturated and unsaturated

A

saturated = compound containing single bonds only
unsaturated = compound containing one or more double (or multiple) bonds

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36
Q

define ion

A

charged particle

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37
Q

2 properties of metal wire used in flame test

A

high melting point, unreactive

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38
Q

why is platinum wire sometimes used in flame test

A

high melting point, is unreactive and doesn’t produce a colour in a flame itself

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39
Q

state why wire should be clean when used in flame test

A

to get rid of impurities that could affect reliability of the results or give a false positive

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40
Q

describe noble gas properties
why do they have low melting/boiling points

A

properties = monoatmoic, colourless gas
full outer shells = This electronic configuration is extremely stable so these elements are unreactive and are inert

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41
Q

what do the period and group signify on periodic table

A

period = number of shells
group = number of electrons in outer shell

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42
Q

define atom, element, compound and mixture

A

atom = smallest part of an element which still behaves as that element
element = substance made up of only one type of atom
compound = substance made up of more than one type of atom chemically bonded together
mixture = Different types of particles in the same physical space but not chemically joined

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43
Q

what is the anion and cation

A

anion = negatively charged ion
cation = positively charged ion

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44
Q

colours formed in flame test for cations:
Li+
Na+
K+
Ca2+
Cu2+

A

Li+ is red
 Na+ is yellow
 K+ is lilac
 Ca2+ is orange-red
 Cu2+ is blue-green

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45
Q

describe a flame test

A

Dissolve the unknown solid in water
2. Soak a splint in the solution
3. Put the splint into the non-luminous flame of the Bunsen burner
4. Observe the colour of the flame

Non- luminous flame as orange can affect results

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46
Q

Describe a chemical test for ammonium ions

A
  1. Add sodium hydroxide solution (NaOH(aq)) and warm.
  2. Put damp red litmus paper in the mouth of the test tube
  3. As ammonia gas (NH3(g)) is produced and it is an alkaline gas the damp red litmus paper turns blue.
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47
Q

Describe a test for Cu2+, Fe2+ and Fe3+

A
  1. Add sodium hydroxide solution (NaOH(aq)) and a precipitate is produced
    Cu2+ = copper( II) hydroxide forms which is a blue precipitate
    Fe2+ = iron(II) hydroxide forms which is a green
    precipitate . . If left it forms a brown precipitate (iron(III) hydroxide) around the top of the solution.
    Fe3+ = iron(III) hydroxide forms which is a brown
    precipitate
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48
Q

Describe test for halide ions –> Cl-, Br-, I-

A

1.Add dilute nitric acid (HNO3(aq)) to make it acidic.
2. Add silver nitrate solution (AgNO3(aq)) and a precipitate is observed.
Cl- = Silver chloride forms which is a white precipitate
Br- = silver bromide forms which is a cream precipitate
I- = silver iodide forms which is a yellow precipitate

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49
Q

Why is dilute nitric acid added?

A

to remove any carbonates and / or hydroxides that may form precipitates and interfere with the results

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50
Q

Describe a test for carbonates (CO3 2-)

A

1.Add dilute nitric acid (HNO3(aq)) and carbon dioxide (CO2(g)) is produced (effervescence is observed).
2.You can test for carbon dioxide by bubbling the gas through limewater which goes cloudy (milky).

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51
Q

Describe a test for sulfates (SO4 2-)

A
  1. Add dilute nitric acid (HNO3(aq)) to make it acidic.
    2.Add barium chloride solution (BaCl2(aq)) and a white precipitate of barium sulfate (BaSO4(s)) is observed.
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52
Q

test for hydrogen H2

A

Add a lit splint to the mouth of the container that contains the gas to be tested and if it produces a squeaky pop it is hydrogen

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53
Q

test for oxygen O2

A

Add a glowing splint to the mouth of the container that contains the gas to be tested and if the splint relights it is oxygen

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54
Q

test for carbon dioxide CO2

A

Bubble the gas through limewater and if the limewater goes cloudy (milky) it is carbon dioxide

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55
Q

test for ammonia NH3

A

Add a damp strip of red litmus paper to the mouth of the container that contains the gas and if the litmus paper turns blue it is ammonia

56
Q

test for chlorine Cl2

A

Add a damp strip of (red or blue) litmus paper to the mouth of the container that contains the gas, if the litmus paper is bleached white it is chlorine

57
Q

describe a test for the presence of water using anhydrous copper(II) sulfate

A

Addthe substance to (white) anhydrous copper(II) sulfate and if the substance is water, then the white solid will turn blue to form hydrated copper(II) sulfate CuSO4 + 5 H2O ⇌ CuSO4.5H2O(s)

58
Q

What happens if you heat blue hydrated copper(II) sulfate strongly?

A

the solid turns white to form
anhydrous copper(II) sulfate This is a reversible reaction. Reversible reactions can take
place in both directions

59
Q

problems caused by disposal of addition polymers

A
  1. toxic greenhouse gases produced -> global warming
  2. landfill sites getting full
60
Q

dot and cross diagram for nitrogen (N2)

A

2 circles of N
6 electrons in middle
2 on outside on each side

61
Q

explain why C60 fullerene has a much lower melting point than graphite

A
  1. graphite is giant covalent
  2. lots of energy required to melt graphite and break bonds
  3. C60 is simple molecular
  4. weak intermolecular forces of attraction overcome easily
  5. more energy required to break strong covalent bonds in graphite than weak intermolecular forces in C60
62
Q

can a mixture melt over a range of temperatures

A

yes

63
Q

a pure substance has a ____ melting and boiling point

A

fixed

64
Q

percentages of 4 most abundant gases in air

A

21 % = oxygen O2
78.1 % = nitrogen N2
0.9% = argon Ar
0.04 % = carbon dioxide CO2

65
Q

define corrsoion

A

chemical reaction between a metal and oxygen in the air

66
Q

define redox reaction

A

reaction in which both reduction and oxidation are happening

67
Q

define rusting

A

chemical reaction between iron and oxygen and water from the air in which rust (hydrated iron(III) oxide) is formed

68
Q

Gas :
arrangement, movement and energy of particles

A

Arrangement: Particles are far apart and there are no forces between them.

Movement: Particles are free to move.

Energy: Particles have more kinetic energy than liquids and solids.

69
Q

Liquid :
arrangement, movement and energy of particles

A

Arrangement: Particles are close together but irregular.

Movement: Particles are free to move.

Energy: Particles have less kinetic energy than gasses but more than solids.

70
Q

Solid :
arrangement, movement and energy of particles

A

Arrangement: Particles are close together and regularly packed.

Movement: Particles vibrate around a fixed point.

Energy: Particles have less kinetic energy than both liquids and gasses

71
Q

gas to solid
solid to gas

A

sublimation

72
Q

solid -> liquid
liquid -> gas
gas-> liquid
liquid-> solid

A

melting
evaporating
condensing
freezing

73
Q

when sodium oxide is heated, it reacts to form sodium metal and sodium peroxide, Na2O2

Complete equation

A

2 Na2O –> Na2O2 + 2Na

74
Q

physical test for pure water

A

test the boiling or freezing point
100 degrees or 0 degrees

75
Q

define rate of reaction

A

A measure of change in concentration of a reactant (or product) with time. The greater the change in concentration over a particular time the faster the rate of the reaction

76
Q

define catalyst

A

substance that speeds up a chemical reaction but which is chemically unchanged at the end of the reaction

77
Q

how does a catalyst work

A

A Catalyst works by providing an alternative pathway with lower activation energy

78
Q

describe Properties of Simple Molecular Substances
boiling point high or low?
conducts electricity?

A

Simple molecular structure.
* Weak intermolecular forces of attraction between the molecules.
* These require little energy to overcome them (break)
* Therefore these substances have low melting points.

  • Simple molecular structure
  • there are no charged species that are free to move so the substance will not conduct electricity
79
Q

describe Properties of Giant Ionic structures:
boiling point high or low?
conducts electricity?

A

Giant ionic structure (ionic bonds)
 Strong ionic bonds (strong electrostatic forces of attraction between oppositely charged ions) are broken
 The strong bonds require lots of energy to break them.

Giant ionic structure (ionic bonds)
 The ions are free to move when the ionic compound is molten/in solution, but not in solid form when the ions are fixed in position and cannot move.

80
Q

Explain why sodium oxide does not conduct electricity
(sodium oxide is ionic (because compound of metal and non-metal)

A

Particles are in a fixed position, so no free moving electrons that can carry current

oppositely charged ions - extra electrons in outer shells gained or lost to form full outer shell - so no free moving electrons

81
Q

4 factors affecting rate of reaction

A
  1. surface area of reactant
  2. concentration of reactant
  3. temperature
  4. adding a catalyst
82
Q

Why does increasing the surface area of a solid reactant increase the rate of a reaction?

A

More particles of the solid are exposed on the surface so there are more successful collisions per unit time.

83
Q

what does concentration of a solution tell us?

A

how much solute is dissolved in a given volume of solvent

84
Q

Why does increasing the concentration of a solution of increase the rate of reaction?

Why does increasing the pressure of a gas increase the rate of a reaction?

A
  1. There are more particles per unit volume so more successful collisions per unit time.
  2. There are more particles per unit volume (allow particles are closer together) so more successful collisions per unit time.
85
Q

Why does increasing the temperature increase the rate of a reaction?

A

Particles move faster so there are more successful collisions per unit time. Particles also have more energy so more of those collisions (more collisions per unit time) have energy greater than the activation energy.

86
Q

Explain why adding a catalyst increases the rate of a reaction.

A

A catalyst provides an alternative reaction route of lower activation energy so more collisions (or particles) have energy greater than the activation energy.

87
Q

3 methods to prevent iron rusting

A
  1. barrier methods
  2. galvanising
  3. sacrificial protection
88
Q

how rusting is prevented by barrier methods

A

Rusting may be prevented by stopping the water and oxygen getting to the iron with a barrier of grease, oil, paint or plastic.

89
Q

how rusting is prevented by galvanising (coating in zinc) - alloying - only iron can rust

A

(coating in zinc) also prevents water and oxygen getting to the iron, but with galvanising even if the barrier is broken the more reactive zinc corrodes before the less reactive iron. During the process, the zinc loses electrons to form zinc ions.

90
Q

how rusting is prevented by sacrificial protection

A

Oxygen reacts with other metal first

91
Q

incomplete combustion equation (balanced)

A

octane + oxygen –> carbon + carbon monoxide + water

92
Q

how does simple distillation work

A

Simple distillation is used to separate a solvent from a solution. It is useful for producing water from salt solution.

Simple distillation works because the dissolved solute has a much higher boiling point than the solvent. When the solution is heated, solvent vapour evaporates from the solution. The gas moves away and is cooled and condensed. The remaining solution becomes more concentrated in solute as the amount of solvent in it decreases.

93
Q

what happens when bromine water reacts with an alkene

A

colourless product formed
bromine water goes from orange to colourless

94
Q

name of reaction to test for alkenes and the condition needed

A

addition reaction
needs to occur in dark

95
Q

give the balanced chemical equation for the reaction of ethene and bromine water

A

C2H4 + Br2 –> C2H4Br2
(gets rid of alkene double bond)

96
Q

give name of product formed

A

1, 2 Dibromoethane

97
Q

give the balanced chemical equation for the reaction of but-2-ene and bromine water

A

C4H6 + Br2 –> C4H6Br2

98
Q

give name of product formed

A

1, 2 Dibrobutane

99
Q

what happens if bromine reacts with an alkane?condition?

A

orange -> brown
substitution reaction
UV light

100
Q

give the balanced chemical equation for the reaction of methane with bromine in the presence of UV light

A

CH4 + Br2 —————> CH3Br + HBr
UV light

101
Q

give the name of product(s) formed

A

bromoethane + hydrogen bromide

102
Q

alkane reacts with bromine, alkene reacts with ____________

A

bromine water

103
Q

give the name of product(s) formed

A

bromoethane + hydrogen bromide

104
Q

give the balanced chemical equation for the reaction of methane with bromine in the presence of UV light

A

C3H8 + Br2 —————> C3H7Br + HBr
UV light

105
Q

give name of product(s) formed

A

1 bromoproane + hydrogen bromide

106
Q

equation for rust

A

iron + oxygen –> hydrated iron (II) oxide

107
Q

what has been oxidised in equation

A

iron -gained oxygen, lost electrons

108
Q

half equation for iron (III) ions involved

A

Fe –> Fe3+ + 3e-

109
Q

define addition polymerisation

A

The process of joining many small monomers to form one long polymer chain

110
Q

define monomer and polymer

A

monomer - small molecule that joins together with many other small molecules to form one large polymer
polymer - large molecule formed by the joining many small monomers together

111
Q

sacrificial protection
iron is a better _______ reagent than magnesium
iron gains ________ more ______ than magnesium
Fe3+ + 3e- –> _____
Mg –> _________
iron is _________
magnesium is _______
iron is _________ ________ MAGNESIUM

A

oxidising
electrons, easily
Fe
Mg2+ + 2e-
oxidised
reduced
reduced, before (magnesium rusts before iron, so iron doesn’t rust straight away)

112
Q

rate of reaction =
Units(g/min)

A

1000/time period OR amount of reactant used or amount of product formed/time

113
Q

An investigation of the reaction between marble chips and hydrochloric acid:
calcium carbonate + hydrochloric acid –> calcium chloride + water + carbon dioxide
Give balanced equation

A

CaCO3 (s) + 2HCl (aq) –> CaCl2 (aq) + H2O(l) + CO2(g)

114
Q

how does practical work

A

Marble chips, calcium carbonate (CaCO3) react with hydrochloric acid (HCl) to produce carbon dioxide gas. Calcium chloride solution is also formed.

Using the apparatus shown the change in mass of carbon dioxide can be measure with time.

As the marble chips react with the acid, carbon dioxide is given off.

115
Q

what is the purpose of the cotton wall at top of conical flask

A

to allow carbon dioxide to escape, but to stop any acid from spraying out.

116
Q

describe graph showing this reaction

A
  1. at start, graph is very steep showing lots of carbon dioxide produced per minute - reaction is fast
  2. middle, graph getting less steep, - reaction is showing down
  3. graph becomes horizontal showing that no more carbon dioxide is being reduced - reaction has stopped
117
Q

example of dilution of coloured solutions

A

i) dilution of coloured solutions

Dissolving potassium manganate(VII) in water demonstrates that the diffusion in liquids is very slow because there are only small gaps between the liquid particles into which other particles diffuse.

The random motion of particles cause the purple colour to eventually be evenly spread out throughout the water.

Adding more water to the solution causes the potassium manganate(VII) particles to spread out further apart therefore the solutions becomes less purple. This is called dilution.

118
Q

Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal

The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
COPPER

A

The copper is in excess and uses up the oxygen to form copper oxide (CuO).

All the oxygen in the air is therefore used up, and so the volume of the air decreases by about 20% (the percentage of oxygen in air).

119
Q

Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal

The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
IRON

A

Iron wool in tube is slightly damp
Invert the tube in beaker of water, so tube mouth is covered
Measure the length of column of air
Leave for 1-2 weeks
Use difference/initial x 100 to calculate oxygen in air

The iron reacts with the oxygen in the air (rusting). Mass of iron increases

As long as the iron, oxygen and water are all in excess, the total volume of air enclosed by the apparatus decreases by about a fifth (20%) over several days.

IRON + OXYGEN + WATER –> HYDRATED IRON(III) OXIDE

120
Q

Practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal

The following 3 experiments can be used to determine that oxygen (O2) makes up approximately 20% by volume of air.
PHOSPHORUS

A

The phosphorus is lit with a hot wire.

It reacts with the oxygen in the air and causes the water level in the bell jar to rise by about 20%.

121
Q

alkanes are best fuel because

A

easily ignited

122
Q

use of alkenes

A

to maek polymer - starter material to produce other chemicals

123
Q

why is carbon dioxide bad

A

contributes to global warming as is greenhouse gas

124
Q

describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper(II) carbonate

A

On heating metal carbonates thermal decompose into metal oxides and carbon dioxide
Observation: green powder (CuCO3) changes to a black powder (CuO)

CuCO3 –> CuO + CO2

125
Q

Why is taj mahal changed in appearance after years, as it is made of calcium carbonate and sulfur dioxide is present in the atmosphere

A

Sulfur dioxide into water
Causes acid rain
Erodes limestone as it reacts away the limescale

126
Q

How to know if it is a catalyst

A

Measure mass before and after, if same , it is catalyst

127
Q

what type of structure/ bonding does carbon dioxide have?

A

Simple molecular structure
Covalent bonds

128
Q

Properties of co2

A

Colourless odourless
More dense than air
Fairly soluble in water and used in fizzy drinks, used in fire extinguishers as it displaces oxygen which is needed for fire

129
Q

Why is helium better for balloons than hydrogen

A

Less dense than air
Hydrogen is explosive air

130
Q

3 ways to produce carbon dioxide

A

Burning hydrocarbons
Thermal decomposition of carbonates
Hydrochloric acid + calcium carbonate —> calcium chloride + water + carbon dioxide

131
Q

What type of reaction is rusting?

A

Oxidation

132
Q

What does fractional distillation separate

A

Miscible liquids at different boiling points

133
Q

How is oxides of nitrogen formed in car engines

A

Reacts with oxygen then ignited by spark

134
Q

classify elements as metals by using their electrical conductivity and the acid-base character of oxides

A

Basic oxides (Alkaline) - react to form salt and water
Good conductors of electricity
High melting and boiling point
Malleable

135
Q

classify elements as non-metals by using their electrical conductivity and the acid-base character of oxides

A

Acidic oxides (Acidic/neutral)
does not conduct electricity (except for graphite)
Low melting and boiling point
Flaky

136
Q

TRIPLE AWARD

A

IGCSE Edexcel Chemistry (21 decks)

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