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Relative atomic mass
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177 Terms
1
Relative atomic mass
The average mass of an atom, relative to 1/12 mass of the carbon 12 isotope, with its abundance taken into account.
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2
What are isotopes?
Atoms of the same element with different numbers of neutrons.
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3
Define a mole of a substance
An amount containing Avogadro's number of particles*
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4
State Avogadro's Law
Equal volumes of gases contain equal numbers of molecules under the same conditions
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5
State Charles' Law
Volume of a gas varies directly with temperature
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6
State Boyle's Law
The volume of a gas is inversely proportional to pressure at constant temperature
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7
Define mass number
The sum of the number of protons and neutrons in an atom of an isotope
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8
State Gay-Lussac's Law of Combining Gases
The volumes of reacting gases at the same temperature and pressure, can be represented by whole number ratios
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9
Define electronegativity
The measure of the ability of an atom to attract a shared pair of electrons in a covalent bond
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10
State Le Chatelier's principle
A system at equilibrium will move to oppose stress
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11
Define atomic orbital
A region of space surrounding the nucleus where there is a 99% probability of finding an electron
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12
Define first ionisation energy
The minimum energy needed to remove the most loosely-bound electron from a gaseous atom in its ground state
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13
Define (atomic) Energy level
Discrete energy of an electron
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14
Define radioactivity
Spontaneous emission of alpha, beta, or gamma radiation from an unstable decaying nuclei.
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15
Define atomic radius
Half the distance between the centres of two single-bonded atoms of the same element
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16
What is the series of coloured lines in a line emission spectrum known as?
The Balmer series
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17
What is an ideal gas?
A gas that obeys the gas laws under all conditions
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18
Define bond energy
Average energy required to break one mole of a bond and to separate the atoms
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19
State the Heisenberg uncertainty principle
It is not possible to measure both the position and momentum of an electron simultaneously
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20
Who discovered Cathode rays?
JJ Thompson
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21
Explain the term "Intermolecular forces"
Attractive or repulsive forces between molecules
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22
What is meant by ground state?
An electron in its lowest energy state
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23
Hydrogen "bonding"
the intermolecular force in which a hydrogen atom that is bonded to an atom of NOF is attracted to a lone pair of another electronegative molecule
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24
Dipole-dipole interaction
an attraction between regions of polar molecules that have partial charges of opposite sign
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25
Van der Waals Forces
a slight, brief attraction that develops between the oppositely charged regions of nearby molecules
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26
Define second ionisation energy
The energy required to remove an electron from a monopositive atom in its ground state
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27
State Aufbau principle
An electron occupies the lowest-energy orbital first in its ground state
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28
State the Pauli exclusion principle
Maximum of 2 electrons may occupy an orbital and they must be of opposite spin
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29
State Hund's rule of maximum multiplicity
states that when two or more orbitals of
equal energy are available, they fill them single before fully.
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30
Define octane number
A measure of the tendency of a fuel to resist knocking
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31
activation energy
minimum energy required for colliding particles to react
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32
aliphatic compound
organic compound that consists of open chains of carbon atoms and ring compounds that resemble them in chemical properties
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33
Alkane
a hydrocarbon containing only single covalent bonds
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34
Alkenes
hydrocarbons that contain only one double carbon-carbon bond
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35
alkynes
hydrocarbons which contain only one carbon-carbon triple bond
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36
amphoteric substance
substance which can act as either an acid or a base e.g water
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37
Anion
A negatively charged ion attracted to the anode
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38
anode
Positive electrode
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39
cation
A positively charged ion attracted to the cathode
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40
cathode
Negative electrode
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41
aromatic compounds
substances containing a benzene ring
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42
Atomic number
the number of protons in an atom
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43
Atomic orbit
fixed path of an electron around the nucleus of an atom
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44
Sublevel
subdivision of an atomic orbit (main energy level) and consists of one or more orbitals of the same energy
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45
Autocatalysis
catalysis of a reaction by one of the products of that reaction
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46
Biochemical Oxygen Demand (BOD)
the amount of oxygen consumed when a sample of water is kept in the dark at 20°C for five days
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Bronsted-Lowry acid
proton donor
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48
Bronsted-Lowry base
proton acceptor
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Bronsted-Lowry strong acid
good proton donor
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50
Bronsted-Lowry weak acid
poor proton donor
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51
Arrhenius acid
substance that dissociates in water to produce H+ ions
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52
Arrhenius base
substance that dissociates in water to produce OH- ions
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53
Esterification
The reaction of an alcohol with a carboxylic acid to produce an ester and water.
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54
Eutrophication
nutrient enrichment in lakes caused by heavy metal ions in polluted water leading to algal bloom (algae overgrowth)
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55
Excited state
electrons at higher energy levels than ground state
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Exothermic reaction
Reaction that releases heat
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57
Endothermic Reaction
Reaction that absorbs heat
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Saponification (Base Hydrolysis)
A variation on esterification where a long chain Organic Acid reacts with a base to produce a Soap molecule (metal salts of fatty acids)
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hydrolysis reaction
A chemical reaction that breaks apart a larger molecule by adding a molecule of water
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60
addition reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
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elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
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substitution reaction
a reaction in which one or more atoms replace another atom or group of atoms in a molecule
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Screening (of drinking water)
water passed through a wire mesh to remove floating debris
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flocculation
addition of a flocculating agent to water to cause clumping (coagulation) of suspended solids
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sedimentation
water passed into bottom of settlement tanks, rises up slowly and clear water decants into channels, solids remain at base
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Chlorination
chlorine added to water to sterilise it (kill micro-organisms)
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fluoridation
adding flourine to drinking water to reduce tooth decay and strengthen enamel
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Primary treatment of sewage
large solids removed by screened and suspended solids removed by sedimentation
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secondary treatment of sewage
decomposition of sewage pollutants by micro-organisms
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70
tertiary treatment of sewage
removal of phosphorus compounds by precipitation and removal of nitrogen compounds by ion-exchange or denitrifying bacteria
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71
principle of colorimetry
amount of absorbance of light by a coloured solution is proportional to the concentration of the solution
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72
feedstock
Raw materials needed for a chemical manufacturing process.
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73
fractional distillation
separation of crude oil into different compounds by boiling point differences
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74
octane number
measure of the ability of a fuel to resist auto-ignition
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75
EDTA
ethylenediaminetetraacetic acid
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76
MTBE
Methyl Tertiary Butyl Ether
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ways to increase octane number
Dehydrocyclisation, isomerisation, catalytic cracking, addition of oxygenates
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78
Heterogenous catalysis
catalysis where reactants and catalyst are in different phases
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79
functional group
group of atoms within a molecule that allows that molecule to be identified
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80
ground state
electrons at lowest energy state
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81
hard water
water that contains calcium or magnesium ions in it that does not easily form a lather with soap and forms scum
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82
heat of combustion
energy released when one mole of a substance is burned completely in excess oxygen
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83
heat of formation
energy change when one mole of a substance is formed from its reactants in their ground states
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heat of reaction
energy change in a chemical reaction according to the equation
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heat of neutralisation
The heat change when one mole of H+ ions from an acid reacts with one mole of OH- ions from a base.
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86
Hess's law equation
∆Hr = Σ∆HfP - Σ∆HfR
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87
Oxidising agent
Substance that causes oxidation and it itself is reduced
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Oxidation
loss of electrons, increase in oxidation number, increase in oxygen
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Reducing agent
substance that causes reduction and it itself is oxidised
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reduction
gain of electrons, decrease in oxidation number, decrease in oxygen
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temporary hardness
water hardness that can be removed by boiling the water
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permanent hardness
water hardness that cannot be removed through boiling
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methods of removing hardness
boiling, distillation, Washing soda (Na2CO3), ion-exchange resin
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94
complexometric titration
titration involving formation of complex between metal ions and a reagent e.g edta
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buffer solution
solution that resists changes in pH
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96
carbonium ion
Unstable positive carbon intermediate
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97
Primary standard
substance that is pure, stable, does not sublime, can be used to make up a standard solution, does not effervesce
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how is hydrogen gas produced industrially
electrolysis of water, steam reforming
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99
Volatile liquid
a liquid that evaporates readily or at a low temperature
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100
Dalton's atomic theory
All matter is made up of very small particles.
Atoms are individible
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