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chem > chemistry module 3 definitions > Flashcards

chemistry module 3 definitions Flashcards

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1
Q

bohr model

A

small dense positive nucleus with electrons orbiting around

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2
Q

first ionisation energy

A

the removal of one mole of electrons from one mole of gaseous
atoms. Factors which affect the first ionisation energy are: the strength of attraction between
the electron and the nucleus, the nuclear charge and the atomic radius. There is a small
decrease in first ionisation energy due to s- and p-subshell energies (between Be and B) and
p-orbital repulsion (between N and O)

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3
Q

giant covalent lattice

A

a network of atoms bonded by strong covalent bonds (e.g. carbon
(diamond, graphite and graphene) and silicon). Giant covalent lattices typically insoluble with
a high melting and boiling point due to the presence of strong covalent bonds. They are also
poor electrical conductors as they don’t contain mobile charged particles

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4
Q

giant metallic lattice structure

A

the structure of all metals, made up of cations and
delocalised electrons. Giant metallic structures are typically insoluble with a high melting and
boiling points due to strong electrostatic forces of attraction between cations and electrons.
Metals are good electrical conductors due to the presence of delocalised electrons (mobile
charges).

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5
Q

group

A

column

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6
Q

period

A

row

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7
Q

metallic bonding

A

strong electrostatic attraction between cations and delocalised electrons

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8
Q

p block

A

the part of the periodic table which have their highest energy electron in a p orbital (same for s, f and d orbital if u just switch stuff out)

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9
Q

periodicity

A

a repeating trend in physical and chemical properties across the periods of the
periodic table

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10
Q

successive ionisation energies

A

the energy required to remove each electron one-by-one
from one mole of gaseous atoms / ions

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11
Q

base

A

a substance that can accept H+
ions from another substance. Group 2 compounds can
be used as bases: Ca(OH)2
is used to neutralise acidic soils in agriculture and Mg(OH)2
and
CaCO3
are used as antacids to treat indigestion

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12
Q

electron configuration

A

the arrangement of electrons into orbitals and energy levels around
the nucleus of an atom/ ion. Group 2 elements have an s2
outer shell electron configuration

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13
Q

group 2 oxides

A

a compound with the general formula MO, where M is a group 2 element.
When group 2 oxides react with water, they form an alkaline solution, with alkalinity
increasing down the group

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14
Q

oxidation

A

-loss of electrons
-increase in oxidation number

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15
Q

reduction

A

-gain of electrons
-decrease in oxidation number

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16
Q

second ionisation energy

A

the removal of one mole of electrons from one mole of gaseous
1+ ions to form one mole of 2+ ions.

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17
Q

boiling point

A

the temperature at which a liquid boils and becomes a gas. Boiling point
increases down group 7 due to the increasing strength of London Forces between the
halogen molecules.

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18
Q

diatomic molecules

A

molecules made up of 2 atoms. halogens and oxygen are diatomic. if there aren’t 2 then there will be a free radical

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19
Q

displacement reaction

A

a reaction in which one atom is replaced by another. Halogens can
undergo displacement reactions as their reactivity decreases down the group. The more
reactive halogen will displace the less reactive halogen from a solution of its salt.

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20
Q

disproportionation reaction

A

wherein the same element is both oxidised and reduced and this happens in chlorination where chlorine is added to water to purify it and reaction between chlorine and cold, dilute aqueous sodium hydroxide to form bleach

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21
Q

electron configuration

A

the arrangement of electrons into orbitals and energy levels around
the nucleus of an atom / ion. The halogens have a s2p
5
outer shell electron configuration.

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22
Q

precipitation reaction

A

a reaction in which two aqueous solutions are combined to form an
insoluble salt (a precipitate). Halide anions undergo precipitation reactions with aqueous
silver ions

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23
Q

water treatment

A

the addition of chlorine to water to kill bacteria. The risks associated with
the use of chlorine to treat water are the hazards of toxic chlorine gas and the possible risks
from the formation of chlorinated hydrocarbons

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24
Q

anion

A

negatively charged ion

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25
Q

cation

A

positively charged ions

26
Q

ammonium ion

A

an ion with the formula NH4+ . The test for ammonium ions is a reaction with
warm NaOH, which forms NH3

27
Q

carbonate

A

a salt containing the CO3
2- anion. A reaction between a carbonate and H+
will
form CO2
(g)

28
Q

halide

A

a salt containing a group 7 anion. Cl-
, Br-
and I-
can be tested for using a solution of
silver ions as this reaction forms a coloured precipitate. The solubility of the precipitate is
then tested using dilute and concentrated ammonia.

29
Q

sulfate

A

a salt containing the anion SO4
2-. A reaction between SO4
2- and Ba2+(aq) will form a
precipitate

30
Q

order of experiments to test for anions

A

1) carbonates
2) sulphates
3) halides

31
Q

carbonates

A

add an acid which would mean it forms co2 so bubble the gas through limewater and it should turn cloudy

32
Q

sulphates

A
  • add dilute hcl
  • add dilute barium chloride or barium nitrate
    -if a white precipitate of barium sulphate forms then sulphates present
33
Q

halides

A

add silver nitrate ions
cl= white
br= cream
iodide= yellow

34
Q

hallide test alt

A

add dilute ammonia
- if dissolves then its a chloride
add conc ammonia
- if dissolves then its a bromide

if nothing then iodide

35
Q

test for ammonium ions

A

Add a few drops of dilute sodium hydroxide solution, then warm gently. Ammonia gas is produced if ammonium ions are present. damp red litmus paper should turn blue if they are present as ammonia is an alkali

36
Q

activation energy

A

the minimum energy required for a reaction to take place

36
Q

average bond enthalpy

A

the energy required to break one mole of gaseous bonds. Actual
bond enthalpies may differ from the average as the average bond enthalpy considers a
particular bond in a range of molecules

37
Q

endothermic

A

a reaction which takes in energy (ΔH is positive). More energy is required to
break bonds than is released by making bonds. energy of reactants > products

38
Q

exothermic

A

a reaction which gives out energy (ΔH is negative).More energy is released by making bonds that are needed to make them. energy of reactants< energy of products

39
Q

enthalpy (H)

A

a value that represents the heat content of a system

40
Q

enthalpy change (ΔH)

A

the change in the heat content of a system during a reaction. This
can be determined from experimental results using q = mcΔT (where q is the heat change of
the surroundings, m is the mass of the surroundings, c is the specific heat capacity and ΔT is
the change in temperature).

41
Q

enthalpy change of combustion

A

the enthalpy change that takes place when one
mole of a substance is completely combusted.

42
Q

enthalpy change of formation

A

the enthalpy change that takes place when one mole
of a compound is formed from its elements

43
Q

enthalpy change of neutralisation

A

the enthalpy change that takes place when
one mole of water is formed from a neutralisation reaction.

44
Q

enthalpy change of a reaction

A

the enthalpy change that is associated with a
particular chemical equation.

45
Q

enthalpy profile diagram

A

shows the difference in the enthalpy of reactants and products
as well as the activation energy of a reaction

46
Q

hess’ law

A

the enthalpy change of a reaction is independent of the route it takes

47
Q

standard conditions

A

a pressure of 100 kPa and a temperature of 298K.

48
Q

standard states

A

the physical state (s, l, g, aq) of a substance under standard conditions.

49
Q

boltzmann distribution graoh

A

a graph showing the distribution of the energies of molecules in
relation to the activation energy. Increasing temperature will increase the proportion of
molecules with energy above the activation energy. A catalyst lowers the activation energy
meaning more molecules will have sufficient energy to react.

50
Q

catalyst

A

: a substance that speeds up the rate of a reaction without being used up. A catalyst
allows the reaction to proceed via a different route with a lower activation energy. Catalysts
are important in terms of economics and sustainability as they enable processes to take
place at lower temperatures meaning less energy is required (this decreases the combustion
of fossil fuels so CO2
emissions are reduced).

51
Q

collision theory

A

the theory which states that molecules must collide with sufficient energy
at the correct orientation for a reaction to occur

52
Q

concentration

A

: the amount of a substance that is dissolved per unit volume of solution.
Increasing the concentration increases the rate of reaction as there are more molecules in
the same volume meaning more frequent successful collisions.

53
Q

enthalpy profile diagram

A

shows the difference in the enthalpy of reactants and products
as well as the activation energy of a reaction.

54
Q

heterogeneous catalyst

A

a catalyst that is in a different state to the reactants (e.g. a solid
catalyst with gaseous reactants)

55
Q

homogeneous catalyst

A

a catalyst which is in the same state as the reactants.

56
Q

pressure

A

the force that a gas exerts on the walls of a container. Increasing the pressure
increases the rate of reaction as there are more molecules in the same volume (or the same
number of molecules in a smaller volume) meaning more frequent successful collisions.

57
Q

rate of reaction

A

a measure of how quickly a reactant is used up/ a product is formed. Rate
can be determined by measuring concentration, the volume of gas produced or the mass lost
over time.

58
Q

compromise

A

balancing several different factors in order to get the best possible outcome.
In industry, the position of the equilibrium and rate of reaction must be considered when
deciding the conditions for the reaction. These factors must also be balanced with safety and
economics

59
Q

dynamic equilibrium

A

a closed system in which the rates of the forward and reverse
reactions are equivalent. The concentrations of reactants and products don’t change

60
Q

le chatelier’s principle

A

when a system in dynamic equilibrium is subject to change, the
position of equilibrium will shift to minimise the change. This principle is used to determine
the effect of changing pressure, temperature or concentration on the position of equilibrium

61
Q

kc

A

the equilibrium constant that is equal to the concentration of products raised to their
stoichiometric coefficients divided by the concentration of reactants to the power of their
stoichiometric coefficients. When KC
is greater than 1, the equilibrium favours the products.
When KC
is less than 1, the equilibrium favours the reactants.

chem (7 decks)

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