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

Module 3 - Periodic Table And Energy Flashcards

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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
Q

carbonate test

A

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

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26
Q

sulphate test

A

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
Q

halide test

A

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
Q

correct order when carrying out testing for ions tests

A

carbonate test
sulphate test
halide tests

29
Q

testing for ammonium ions

A

add aq NaOH, mixture is warmed and ammonia ions released , lay moist indicator paper and if ammonia present paper will turn blue

30
Q

whats enthalpy

A

a measure of the heat energy in a chemical system . enthalpy cannot be measured but enthaply changes can

31
Q

enthalpy change equation

A

delta H = products - reactants

32
Q

where does heat move in endo and exo reactions

A

exo- from the system to surroundings
endo- from the surroundings to the system

33
Q

activation energy

A

the minimum energy required for a reaction to take place

34
Q

standard conditions in enthalpy

A

pressure- 100kpa or 101kpa or 1atm
temp- 298k or 25c
conc- 1 moldm-3
in standard states

35
Q

enthalpy change of reaction

A

the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard states and conditions

36
Q

enthalpy change of formation

A

the enthalpy change that takes place when one mole of a compound is formed from its elements under standard states and conditions

37
Q

enthalpy of combustion

A

the enthalpy change that takes place when 1 mole of a substance is completely reacted with o2 under standard states and conditions

38
Q

enthalpy of neutralisation

A

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
Q

specific heat capacity

A

the energy required to raise the temperature of 1g of a substance by 1k.
for water its 4.18 g-1 K-1

40
Q

heat energy equation (Q)

A

q= m x c x temp change

41
Q

why is the experimental values for standard enthalpy of combustion not accurate

A
  • 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
Q

whats average bond enthalpy

A

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
Q

is energy released when bonds form endo or exo

A

exo

44
Q

standard enthalpy of reaction equation

A

sum of reactant bond enthalpies - sum of products bond enthalpies

45
Q

what does hess’ law state

A

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
Q

what is meant by rate of reaction + equation for rate

A

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
Q

things that alter the rate of reaction

A

conc
temp
catalyst
surface area

48
Q

how does an increase in conc increase rate of reaction

A

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
Q

whats a homogenous catalyst

A

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
Q

heterogeneous catalysts

A

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
Q

whats the y axis on the boltzmann curve

A

number of particles with a given energy

52
Q

whats the x axis on the boltzmann curve

A

energy

53
Q

effect of temperature on the boltzmann distribution

A

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
Q

what does a catalyst provide

A

an alternate route with a lower activation energy where more particles can react successfully

55
Q

in a dynamic equilibrium system..

A

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
Q

le chateliers principle

A

states that when a system in equilibrium is subjected an external change the system readjusts itself to minimise the effect of that change

57
Q

effects of concentration changes on the equilibrium

A

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
Q

change in the position of equilibrium due to temperature

A

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
Q

the effects of pressure on the equilibrium

A

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
Q

kc equation

A

kc = prod/ react

61
Q

what does kc value tell us

A

indicates the relative proportions of reactants and products in the equilibrium system

62
Q

what does a kc value of 1 tell us

A

indicates the position of equilibrium that is halfway between reactants and products

63
Q

what does a kc value of over 1 tell us

A

indicates a position of equilibrium that is towards the products

64
Q

what does a kc value of less than 1 tell us

A

indicates a position of equilibrium that is towards the reactants

Chemistry A Level (12 decks)

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