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Chemistry A Level > Module 3 - Periodic Table And Energy > Flashcards

Module 3 - Periodic Table And Energy Flashcards

1
Q

Ionisation energy definition

A

Measures how easily an atom loses electrons to form positive ions

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2
Q

First ionisation energy

A

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.

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3
Q

Factors affecting ionisation energy

A
  • atomic radius
  • nuclear charge
  • electron shielding
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4
Q

Why does atomic radius affect the ionisation energy

A

The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction. The force of attraction falls off sharply with increasing distance, so atomic radius has a large effect

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5
Q

How does nuclear charge affect ionisation energy

A

The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons

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6
Q

How does electron shielding affect ionisation energy

A

Electrons are negatively charged and so inner-shell electrons repel outer-shell electrons. This repulsion, called the shielding effect, reduces the attract between the nucleus and the outer electrons

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7
Q

Second ionisation energy

A

The energy required to remove one electron from each atom in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions

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8
Q

Metallic bonding

A

The strong electrostatic attraction between cations and delocalised electrons

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9
Q

Properties of metals

A

High electrical conductivity
High melting and boiling points
Not soluble

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10
Q

Properties of giant covalent structures

A

High mtp and btp as strong covalent bonds present
Insoluble in almost all solvents
Non-conductors of electricity ( only exceptions being graphene and graphite)

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11
Q

Why does carbon (diamond) and silicone conduct electricity

A

All 4 outer-shell electrons are involved in covalent bonding, so non available for conducting electricity

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12
Q

Why can graphene and graphite conduct electricity

A

Only 3 of the 4 outer-shell electrons are used in covalent bonding. The remaining electrons are released into a pool of delocalised electrons shared by all atoms in the structure

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13
Q

Metal + acid —>

A

Salt + hydrogen

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14
Q

Reactions of group 2 compounds with water

A

Hydroxide ions are released forming alkaline solutions of the metal hydroxide. When the solution is saturated any further metal and hydroxide ions will form a solid precipitate

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15
Q

Solubility of hydroxides with group 2 compounds

A

The solubility of the hydroxides in water increases down the group resulting solutions contain more OH- and are more alkaline

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16
Q

How are group 2 compounds used in agriculture

A

Ca(OH)2 is added to fields as lime by farmers to increase the Ph of acidic soils . The calcium hydroxide neutralises acid in the soil forming neutral water

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17
Q

Reaction colour of I2 in cyclohexane compared to water

A

Water = brown
Cyclohexane = violet

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18
Q

Reaction colour of br2 in cyclohexane and water

A

Water = orange
Cyclohexane = orange

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19
Q

Reaction colour of cl2 in cyclohexane and water

A

Water = pale green
Cyclohexane = pale green

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20
Q

Reaction between I- and cl2 and br2

A

I- displaces cl2 and Br p2 forming i2 so a violet layer forms

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21
Q

Reactions between br- and cl2 and I2

A

Br- displaces cl2 and forms br2 meaning mixture turns orange
No reaction takes place between Br- and i2

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22
Q

Reactivity trend down group 7

A

Atomic radius increases, more inner shells so shielding increases
Less nuclear attraction to capture an electron from another species
So reactivity decreases

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23
Q

What’s a disproportionating reaction

A

A redox reaction in which the same element is both oxidised and reduced

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24
Q

benefits and risks of chlorine

A

ensures water is fit to drink and bacteria is killed but chlorine is extremely toxic gas

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25
carbonate test
carbonates react with acids to form co2. so add HNO3 and bubble should form. now run the bubbles through Ca(OH)2 , a white precipitate forms if CO2 is present which turns lime water cloudy
26
sulphate test
add barium nitrate or barium chloride to solution (use barium nitrate if your going to do halide test after) and a white preciptate will form if sulphate is present
27
halide test
add aqueous silver nitrate. chloride= white precipitate bromide= cream precipitate iodide= yellow precipitate now add NH3 to check chlorine will disolve in dilute and bromine will dissolve in con NH3 but iodide wont dissolve at all
28
correct order when carrying out testing for ions tests
carbonate test sulphate test halide tests
29
testing for ammonium ions
add aq NaOH, mixture is warmed and ammonia ions released , lay moist indicator paper and if ammonia present paper will turn blue
30
whats enthalpy
a measure of the heat energy in a chemical system . enthalpy cannot be measured but enthaply changes can
31
enthalpy change equation
delta H = products - reactants
32
where does heat move in endo and exo reactions
exo- from the system to surroundings endo- from the surroundings to the system
33
activation energy
the minimum energy required for a reaction to take place
34
standard conditions in enthalpy
pressure- 100kpa or 101kpa or 1atm temp- 298k or 25c conc- 1 moldm-3 in standard states
35
enthalpy change of reaction
the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard states and conditions
36
enthalpy change of formation
the enthalpy change that takes place when one mole of a compound is formed from its elements under standard states and conditions
37
enthalpy of combustion
the enthalpy change that takes place when 1 mole of a substance is completely reacted with o2 under standard states and conditions
38
enthalpy of neutralisation
the energy change that accompanies the reaction of an acid by a base to form 1 mole of H2O under standard states and conditions. always -57Kj mol-1
39
specific heat capacity
the energy required to raise the temperature of 1g of a substance by 1k. for water its 4.18 g-1 K-1
40
heat energy equation (Q)
q= m x c x temp change
41
why is the experimental values for standard enthalpy of combustion not accurate
- heat loss to the surroundings - incomplete combustion - evaporation of alcohol from burner wick (all 3 lead to values being less exothermic) -non- standard conditions
42
whats average bond enthalpy
the energy required to break 1 mole of a specified type of bond in a gaseous molecule . always have positive enthalpy values always endothermic energy is required to break bonds
43
is energy released when bonds form endo or exo
exo
44
standard enthalpy of reaction equation
sum of reactant bond enthalpies - sum of products bond enthalpies
45
what does hess' law state
if a reaction can take place by 2 routes and the starting and finishing conditions are the same the total enthalpy change must also be the same
46
what is meant by rate of reaction + equation for rate
measures how fast a reactant is being used up or how fast a product is being formed . rate = change in conc/ time . units mol dm-3 S-1
47
things that alter the rate of reaction
conc temp catalyst surface area
48
how does an increase in conc increase rate of reaction
as it increases the number of particles in the same volume the particles are closer together and collide more frequently . so in the same period of time there will be more effective/successful collisions
49
whats a homogenous catalyst
it has the same physical state as the reactants. the catalyst reacts with the reactants and forms and intermediate. the intermediate then breaks down to give the product and regenerates the catalyst
50
heterogeneous catalysts
has a different state to the reactants . reactant molecules are absorbed onto the surface of the catalysts where the reaction takes place . after the reaction the product molecules leave the surface of the catalyst by desorption
51
whats the y axis on the boltzmann curve
number of particles with a given energy
52
whats the x axis on the boltzmann curve
energy
53
effect of temperature on the boltzmann distribution
at higher temp more molecules have an energy greater than the activation energy therefore a greater proportion of collisions will lead to a reaction . at higher temp the actual curve is lower and shifted to the right
54
what does a catalyst provide
an alternate route with a lower activation energy where more particles can react successfully
55
in a dynamic equilibrium system..
the rate of the forwards and backwards reaction is the same the conc of reactants and products do not change. both the forwards and backwards reactions are occuring at the same time a closed system
56
le chateliers principle
states that when a system in equilibrium is subjected an external change the system readjusts itself to minimise the effect of that change
57
effects of concentration changes on the equilibrium
if there are more products formed the position of equilibrium will shift to the right if there are more reactants formed the position of the equilibrium will shift to the left
58
change in the position of equilibrium due to temperature
an increase in temp shifts the equilibrium position in the endothermic direction a decrease in temp shift the equilibrium position towards the exothermic direction
59
the effects of pressure on the equilibrium
increasing the pressure of the system will shift the position of equilibrium to the side with fewer moles reducing the pressure on the system decreasing the pressure shifts the position of equi to the side with more gaseous moles
60
kc equation
kc = prod/ react
61
what does kc value tell us
indicates the relative proportions of reactants and products in the equilibrium system
62
what does a kc value of 1 tell us
indicates the position of equilibrium that is halfway between reactants and products
63
what does a kc value of over 1 tell us
indicates a position of equilibrium that is towards the products
64
what does a kc value of less than 1 tell us
indicates a position of equilibrium that is towards the reactants

Chemistry A Level (12 decks)

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