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chemistry > Revision for 21/9/22 > Flashcards

Revision for 21/9/22 Flashcards

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1
Q

alkane general formula

A

CnH2n+2

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2
Q

homologous series

A

a ‘family’ of organic compounds with the same functional group and similar chemical properties

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3
Q

hyrdocarbons

A

compounds that contain only hydrogen and carbon atoms

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4
Q

alkene general formula

A

CnH2n

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5
Q

Fractional distillation

A

Oil is heated to about 350°C and pumped into the bottom of a tall tower called a fractionating column, where it vaporises.

The column is hotter at the bottom and cooler at the top. As the vaporised oil rises, it cools and condenses.

The heavy fractions (containing large molecules) have a high boiling point and condense near the bottom of the column (where they flow out through a pipe).

The lighter fractions (containing small molecules) have a low boiling point and condense near the top of the column (where they flow out through a pipe).

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6
Q

Order of fractional distillation:

A

Liquid Petroleum Gas (LPG) - Short Chain Hydrocarbons
Petrol
Kerosene
Diesel Oil
Heavy Fuel Oil
Bitumen - Long chain hydrocarbons

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7
Q

How is crude oil formed?

A

Crude oil is formed over millions of years from the remains of plankton, which decayed anaerobically in mud under high pressure and temperature.
The mud stopped them from rotting away.
This organic matter turned into crude oil and was stored within rocks.

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8
Q

Formulation

A

A formulation is a mixture that is a useful product (e.g. toothpaste)

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9
Q

Carbon monoxide cause + effects

A

C: insufficient oxygen during combustion
E: carbon monoxide poisoning

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10
Q

Carbon dioxide cause + effect:

A

C: complete combustion of fuels with carbon atoms
E: contributes to global warming (greenhouse gas)

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11
Q

Carbon dioxide cause + effect:

A

C: complete combustion of fuels with carbon atoms
E: contributes to global warming (greenhouse gas)

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12
Q

Nitrogen oxide cause + effect:

A

C: oxidation of atmospheric nitrogen in cars + lorries
E: acid rain

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13
Q

Particulates cause + effect:

A

C: incomplete combustion of fuels containing carbon atoms
E: global dimming

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14
Q

Water vapour cause + effects:

A

C: complete combustion of hydrocarbons
E: greenhouse gas that radiates heat back onto the Earth’s surface

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15
Q

Sulphur dioxide cause + effect:

A

C: combustion of fuels containing sulfur impurities
E: acid rain

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16
Q

Trend in the boiling point of alkanes

A

The boiling point increases as the number of carbon atoms increase
This causes the intermolecular forces to increase as the size of molecules increase

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17
Q

alkene + hydrogen —> ….

A

alkane
(reaction requires a catalyst)

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18
Q

addition reaction

A

when 1 molecule combines with another molecule to form a chain or a long molecule

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19
Q

alkene + water (or steam) —> ….

A

alcohol
(reaction requires high temperatures + a catalyst)

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20
Q

Alkene + bromine —> …..

A

Alkene + bromine —> dibromoalkane

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21
Q

Order of alkanes

A

Methane - my
ethane - energetic
propane - parents
butane - bought
pentane - popsicles

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22
Q

Steam cracking

A

Heat alkanes to vaporize them and mix with steam and then heat to a very high temperature - causes them to split

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23
Q

Catalytic Cracking

A

Heat alkanes to vaporise them then pass over a hot (600–700°C) catalyst - causes it to split

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24
Q

Cracking

A

Thermal decomposition of long chain alkanes into shorter alkanes and alkenes (which are more useful)

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25
Q

Properties of hydrocarbons

A
  • long chain hydrocarbons are extremely viscous
  • short chain hydrocarbons are extremely flammable
  • short chain hydrocarbons have a low boiling point
  • short chain hydrocarbons have a higher volatility (tendency to turn into a gas)
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26
Q

Test for alkenes:

A

add bromine water to a solution of alkenes
(will turn from orange to colourless in the presence of alkenes)

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27
Q

Polymer

A

a large, long chain made from many monomers joined together

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28
Q

monomer

A

small molecule that bonds with other small molecules to form a larger molecule (polymer)

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29
Q

Features of alkenes

A

unsaturated hydrocarbons
more reactive than alkanes (double bond)
can join together to form polymers

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30
Q

Features of alkanes

A

saturated hydrocarbons
form a homologous series
general formula - CnH2n+2

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31
Q

Complete combustion

A

when there are sufficient amounts of oxygen
reaction produces carbon dioxide and water

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32
Q

Describe why sulfur should be removed from petrol

A

burning sulfur produces sulfur dioxide
causes acid rain

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33
Q

how to name poylmers

A

poly(alkene)

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33
Q

how to name polymers

A

poly(alkene)

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34
Q

endothermic reaction

A

gains energy from surroundings

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35
Q

exothermic reaction

A

transfers energy to the surroundings

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36
Q

Why is sulfur dioxide produced in petrol engines

A

petrol contains sulfur impurities (that react with oxygen)

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37
Q

How are nitrogen oxides produced in petrol engines?

A

nitrogen and oxygen react
at high temperatures (inside a petrol engine)

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38
Q

Why is biodiesel carbon neutral

A

CO2 released when burning biodiesel
CO2 is absorbed by crops to grow and produce biodiesel

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39
Q

Ethical + Economic concerns related to biodiesel

A

ethical: uses land that could be used to grow food
economic: causes cost of food to rise

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40
Q

Fermentation of yeast cells

A

glucose —> ethanol + carbon dioxide

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41
Q

Why shouldn’t we use plastic bags?

A

made from crude oil
not biodegradable
use non-renewable resources
litter (could go to landfill)

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42
Q

Explain how different dyes are separated by paper chromatography.

A

solvent moves through the paper
different dyes have different solubilities in the solvent
the different dyes also have different attractions to the paper
so the dyes each move up the paper a certain distance

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43
Q

How does an energy level diagram show that a reaction is exothermic?

A

the products are at a lower energy level than the reactants

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44
Q

How does an energy level diagram show that a reaction is endothermic?

A

the products are at a higher energy level than the reactants

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45
Q

Explain how a catalyst increases the rate of the reaction.

A

a catalyst provides an alternative pathway
with lower activation energy
which increases the number of successful collisions
increases the rate of reaction
(it is also not used up in reaction)

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46
Q

Compound

A

2 or more different elements

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47
Q

mixture

A

2 or more different substances not chemically combined
(use filtration to separate)

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48
Q

molecule

A

2 or more atoms chemically bonded together

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49
Q

law of conservation of mass

A

total mass of products = total mass of reactants

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50
Q

bond breaking = …

A

endothermic (energy is required to break bonds)

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51
Q

bond making = …

A

exothermic (energy is given out when bonds are made)

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52
Q

Energy change equation:

A

energy in - energy out
or
bonds broken - bonds made

53
Q

energy values

A

kJ/mol

54
Q

How would you explain an overall reaction is exothermic?

A

overall the reaction is exothermic
as more energy is given out when new bonds are made
than energy needed to break bonds

55
Q

How would you explain an overall reaction is endothermic?

A

overall the reaction is endothermic
as more energy is taken in when bonds are broken
than the energy given out when new bonds are made

56
Q

enthalpy change =

A

change in energy

57
Q

How would you separate ethanol, water and unreacted ethene?

A

ethene (low boiling point): so cool the mixture to separate it
ethanol and water: place mixture in a round bottom flask and heat with a bunsen burner, the ethanol will boil first (has a lower boiling point), and evaporate up the fractionating column, it then condenses, and is then collected in another tube

58
Q

difference between a smart polymer and a regular polymer

A

a smart polymer can return to its original shape

59
Q

pros of nanoparticles in sun cream

A

better coverage
more protection from the sun’s UV rays

60
Q

cons of nanoparticles in suncream

A

could damage cells in our body
could have harmful effects on the environment

61
Q

why are nanoparticles useful?

A

they have a high SA:V

62
Q

Equation for heat energy

A

Q (in J) = m (in g) x c (j/kg °C) x change in temperature ( °C)

Q = mcΔT

63
Q

How to test for water:

A

use anhydrous cobalt(II) chloride (which is blue)
it turns pink in the presence of water
or
use anhydrous copper (II) sulphate (which is white)
it turns blue in the presence of water

64
Q

collision theory states:

A

in order for particles to react, they have to collide with sufficient energy

65
Q

activation energy

A

the minimum amount of energy needed for a reaction to take place

66
Q

rate of reaction is dependent on

A

frequency of collisions
amount of energy the particles have

67
Q

Greater surface area: volume ratio increases rate of reaction because…

A

increases the frequency of collisions between reacting particles

68
Q

Effect of temperature on rate of reaction:

A

temperature increases
particles gain more energy and move faster
increases the frequency of collisions and particles collide with more energy
increases the number of successful collisions

69
Q

Effects of concentration and pressure on rate of reaction:

A

increased concentration or pressure
results in more particles per unit of volume
increases the frequency of collisions
increases the rate of reaction

70
Q

Required practical: Rate of reaction (black cross)

A

measure out 10cm3 of sodium thiosulphate into a conical flask
place onto a printed black cross
add 10cm3 of hydrochloric acid and swirl the solution
start the stopwatch and look down
stop the stopwatch when you can no longer see the cross
repeat this experiment to calculate a mean
then repeat this experiment for different concentrations of sodium thiosulphate

(PROBLEM: PEOPLE WILL SEE THE CROSS DISAPPEAR AT DIFFERENT TIMES)

71
Q

Required practical: rate of reaction

A

place 50cm3 of hydrochloric acid into a conical flask
attach a bung and gas syringe to the conical flask
then add 3cm strip of magnesium to the acid
start the stopwatch
record the volume of hydrogen gas collected every 10 seconds
repeat this experiment for different concentrations of hydrochloric acid

72
Q

sharing electrons =… bonding

A

covalent bonding
(between non-metals)

73
Q

transferring electrons = … bonding

A

ionic bonding
(usually between metals + non-metals)

74
Q

Properties of ionic compounds

A

high melting and boiling points - lots of energy required to break strong ionic bonds
conduct electricity when molten or dissolved in water - electrons are free to move around

75
Q

Half equations

A

Na —> Na+ + e-
(losing electrons)

Cl- + e- —> Cl
(gaining electrons)

76
Q

oppositely charged ions are attracted to each other by…

A

electrostatic forces

77
Q

Covalent bonds have:

A

strong covalent bonds
weak intermolecular forces

78
Q

Simple molecular substances:

A

small molecules with strong covalent bonds + weak intermolecular forces
e.g. methane, water, ammonia

79
Q

giant covalent structures:

A

graphite
diamond
sulfur dioxide

80
Q

giant covalent structures:

A

graphite
diamond
sulfur dioxide

81
Q

properties of simple molecular substances:

A

low melting and boiling points due to weak intermolecular forces
(these increase as molecules get larger)
don’t conduct electricity - no free electrons

82
Q

Properties of giant covalent structures:

A

atoms are arranged in regular repeating lattices
high melting and boiling points
don’t conduct electricity - don’t have charged particles

83
Q

Explain how a covalent bond holds two atoms together.

A

electrostatic forces of attraction between negative electrons
and the positive charge of the nuclei

84
Q

when you measure gas you measure the…

A

volume of the gas

85
Q

Why may people not want to be near an ammonia factory?

A

risk of explosions - due to the high pressures
risk of fire - due to high temperatures

86
Q

Why is the best yield of ammonia at equilibrium obtained at low temperatures?

A

the reaction is exothermic

87
Q

Why is the best yield of ammonia at equilibrium obtained at high pressure?

A

there are fewer molecules of product than there are
reactants

88
Q

Haber process:

A

take nitrogen from the air and hydrogen from natural gas
pump it into a reactor at 200 atmospheres and 450 degrees celsius and pass over an iron catalyst
some of the gases will react to form ammonia
ammonia has a low bp
so to separate it from the gases
pump the mixture into the condenser
the ammonia will cool down and condense into liquid ammonia

89
Q

Why do we not use pressures higher than 200 atmospheres?

A

expensive to maintain high pressures
high pressures can lead to explosions

90
Q

What happens at dynamic equilibrium:

A

only reactants at the start
forward reaction is really fast - backwards reaction hasn’t started
some products are formed
forward reaction is greater than backwards reaction
forward reaction begins to slows down - backwards reaction speeds up
eventually the rates of the forward reaction = to the rate of the backward reaction
this is dynamic equilibrium

91
Q

Equilibrium

A

when the concentration of products and reactants are constant

92
Q

Use of ammonia:

A

fertiliser
explosives
nylon
nitric acid

93
Q

if the forward reaction is endothermic

A

increases in temperature = increase in products

94
Q

if the forward reaction is exothermic

A

decrease in temperature = increase in products

95
Q

increasing the concentration of the reactants =

A

equilibrium shift in favour of products - to decrease the concentration of reactants

96
Q

decreased pressure favours:

A

side with most gas particles (molecules)

97
Q

increased pressure favours:

A

side with fewer gas particles (molecules)

98
Q

Catalyst and equilibrium

A

catalyst speeds up time taken to reach equilibrium
does not change position of equilibrium

99
Q

dynamic equilibrium takes place in:

A

a closed system - otherwise the products would escape
in certain conditions

100
Q

reversible reaction

A

reaction that can go forwards and backwards

101
Q

allotropes

A

different structural forms of the same element in the same physical state

102
Q

Allotropes of carbon

A

diamond
graphite
fullerene
graphene

103
Q

diamond

A

each carbon atom is covalently bonded to 4 other carbon atoms
strong - giant covalent structure
high melting point

104
Q

Graphite

A

each carbon atom is covalently bonded to 3 other carbon atoms - forms large flat sheets
no covalent bonds between layers - layers can slide over each other - weak forces between layers - hence graphite is soft
have a free delocalised electron - as each atom has one free electron - which can move through the structure - therefore can conduct electricity and heat
high melting point

105
Q

graphene

A

is a single layer of graphite - one cell thick
able to conduct electricity - can be used in electronics

106
Q

fullerenes

A

large cage-like structures
can form cages around drugs and be delivered to specific sites in the body
can be used as industrial catalysts - large SA:V
can be used to strengthen composite material

107
Q

metallic bonding

A

metal-metal
consists of a giant structure of atoms
in a metal, the outer shell electrons on each atom are free to move around - creates a sea of delocalised electrons
the atoms become positive ions and form a strong electrostatic attraction with the negative electrons

108
Q

Properties of giant metallic structures

A

high melting and boiling point - lots of energy needed to overcome strong metallic bonds
good conductors of heat and electricity - the sea of delocalised electrons can carry electrical current + thermal energy
strong
malleable - layers of metal atoms can slide over each other

109
Q

Alloys

A

2 or more different elements
made by mixing together 2 different metals (or non-metal + metal)
usually use metals with different size atoms

110
Q

Properties of alloys

A

harder - the combination of different sized atoms disrupts the regular structure + distorts the layers so layers can no longer slide over each other

111
Q

ammonium nitrate is made from

A

crystallisation

112
Q

Problems with the ball + stick model

A

there are no gaps between ions
no sticks between ions

113
Q

Explain how electricity is conducted in a metal.

A

metal is made up of a giant structure of atoms
with free electrons
that are free to move
so can carry charge

114
Q

Copper alloys

A

Brass (made of copper + zinc)
harder than copper (pure copper is too soft)
used in door fittings and fixtures

Bronze (made of copper + tin)
used in decorative items and ship propellers
tough + resistant to erosion

115
Q

Gold alloys

A

alloyed with copper - for jewellery
can get different shades of ‘gold’
pure gold is soft

116
Q

Reasons why instrumental methods of analysis are used to detect impurities in metals.

A

rapid
accurate

117
Q

negative electrode =

A

cathode

118
Q

positive electrode =

A

anode

119
Q

elements contain

A

1 type of atom

120
Q

Explain how a covalent bond holds 2 atoms together.

A

the electrostatic force of attraction
between a shared pair of negative electrons
and both positive charged nuclei

121
Q

electrolysis

A

break down of ionic compounds using an electric current

122
Q

Electrolyte

A

liquid that contains free to move ions - which is broken by electricity in electrolysis

123
Q

Process of electrolysis:

A

positive ions move to the cathode
negative ions move to the anode
when the ions reach the electrodes
they lose their charge and become elements
at the electrodes, gases may be given off or a metal is deposited

124
Q

why is it difficult to electroplate plastic?

A

it does not conduct electricity (insulator)

125
Q

Why are spoons electroplated?

A

to prevent corrosion (improve lifespan)
to improve appearance

126
Q

Describe the bonding in a metal, and explain why metals conduct electricity.

A

metal is a lattice of positive ions
with negative delocalised electrons
electrostatic force of attraction between positive ions and electrons
electrons are free to move through the metal

127
Q

Why do aluminium ions collect at the negative electrode?

A

they are positively charged
so are attracted to the negative electrode

128
Q

gases covalently bonded together are …

A

simple molecules

129
Q

by lowering the melting point…

A

less energy is needed

chemistry (8 decks)

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