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Chemistry Flashcards

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1
Q

what is the trend in melting point down group 1?

A

melting point decreases down group 1
+ve metal ions increase in size & less charge dense
so delocalised e-s less strongly attracted to +ve metal ions
so less te needed to overcome the weak electrostatic attraction

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2
Q

which group 1 elements float on water?

A

Li, Na, K

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3
Q

properties of group 1 metals that I missed

A

low density
low mp
ductile
malleable

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4
Q

properties of transition metals that I missed

A

can form different ions
form coloured compounds
not very reactive

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5
Q

what is the trend in boiling point down group 7?

A

boiling point increases
molecules increase in size
so stronger forces b/w molecules
more te needed to overcome them

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6
Q

why are group 8 elements unreactive?

A

do not need to lose, gain or share e-s to gain full outer shell
already have full outer shell of e-s

colourless gases

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7
Q

what are the limitations of:
dot & cross diagrams
ball & stick models
2d & 3d representations?

A

d&c: do not show how ions are arranged in space

b&s: cannot see position of e-s / lone pairs

2d: cannot see where ions are located on different layers

3d: not to scale
no information about the forces of attraction b/w ions or the movement of e-s to form the ions

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8
Q

what are the limitations of the particle model in relation to changes of state?

A

it does not show the size and shape of particles or the space b/w particles
it is not to scale
it does not take into account the forces between particles
it shows particles as same size & inelastic
it assumes particles are spheres

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9
Q

what are nanoparticles?

A

particles that are 1nm-100nm in diameter
smaller than typical particles

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10
Q

how does the size of nanoparticles compare with the typical dimensions of atoms & molecules?

A

nanoparticles: 1nm-100nm
typical atoms & molecules:
fine particles >100nm
coarse particles 2500nm-10,000nm

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11
Q

sa:v of nanoparticles?

A

large

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12
Q

what are the uses of nanoparticles?

A

as catalysts
in nanomedicine
in electrical circuits
silver nanoparticles have antibiotic properties

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13
Q

how do properties of nanoparticles relate to their uses?

A

as catalysts: high sa:v ratio
so large area exposed in reaction
so for the same effect, a smaller amount of nanoparticles is needed than larger particles

in nanomedicine: fullerenes (nanoparticles) are v small so can deliver drugs to the inside of cells

in electrical circuits: some conduct electricity so can make tiny components e.g. computer chips

silver nanoparticles have antibiotic properties so are used to make surgical masks & wound dressings

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14
Q

what are the possible risks associated with some nanoparticulate materials?

A

relatively new so effects on our bodies aren’t fully understood
currently not regulated strictly

nanoparticles in sun cream could damage our cells or damage environment when washed into sea

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15
Q

what is the order of elements in the reactivity series?

A

potassium
sodium
lithium
calcium
magnesium
aluminium
carbon
zinc
iron
hydrogen
copper
silver
gold
platinum

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16
Q

reactivity of metals with water or dilute acids is related to

A

the tendency of the metal to form its +ve ion

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17
Q

what is the preparation for testing metal cations?

A

clean metal loop with HCl
heat with Bunsen burner roaring flame

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18
Q

charge of anode vs cathode

A

anode = +ve
cathode = -ve

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19
Q

what is a fuel cell?

A

continually produce a voltage if supplied with:
- constant fuel supply
- oxygen

fuel oxidised electrochemically not by being burned
so the reaction takes place at a lower temp. than combustion

energy is released as electrical energy

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20
Q

describe hydrogen-oxygen fuel cell

A

hydrogen-oxygen fuel cell, hydrogen and oxygen are used to produce a voltage
water is product

overall reaction: hydrogen + oxygen → water
2H2(g) + O2(g) → 2H2O(l)

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21
Q

what are the advantages & disadvantages of fuel cells?

A

advantages:
use of hydrogen-oxygen fuel cells reduces
- carbon dioxide emissions
- air pollution where the car is being driven
- reliance on fossil fuels

disadvantages:
- hydrogen is gaseous at rtp so difficult to store in the car
- fuel cells & electric motors are less durable than petrol engines and diesel engines so not long-lasting
- expensive
- no countrywide network of refuelling stations
- some methods of producing hydrogen fuel release CO2

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22
Q

what is a chemical cell?

A

they use chemical reactions to transfer energy by electricity

the voltage of the cell depends on factors e.g. material electrodes are made from, the substance used as the electrolyte

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23
Q

how can a simple cell be made?

A

by connecting two different metals in contact with an electrolyte

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24
Q

rechargeable vs non-rechargeable cells

A

non-rechargeable: voltage produced until the reactants are used up

rechargeable: chemical reactions can be reversed when an external circuit is supplied

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25
describe the simple electric cell (electrodes coated in 2 different metals)
more reactive metal undergoes oxidation bc it loses electrons readily = it becomes the anode less reactive metal = cathode bc less likely to lose electrons the further apart the metals are in the reactivity series, the greater the voltage of the cell
26
table of steel properties & uses
see camera roll 19/10/24
27
examples of exothermic & endothermic reactions
exothermic: combustion thermite hydration of anhydrous compounds respiration neutralisation displacement metals + acids endothermic: photosynthesis thermal decomposition acid + carbonate reactions electrical decomposition
28
what are the stages that are analysed as part of a life-cycle assessment?
1. making materials for the product from raw materials 2. manufacture the product 3. transporting the product 4. using the product 5. disposing of the product
29
what is analysed at each stage of LCA?
use of raw materials inc. water use of energy release of waste substances into environment
30
what is the impact of each type of disposal on the environment?
landfill - using up land incineration - release of waste gases = pollution recycling - use of energy & production of waste reusing - reduces impact on environment
31
what factors must be considered to evaluate whether recycling is viable?
balancing the use of the raw materials such as finite resources & need to conserve them availability of the material to be recycled issues with collecting the material removal of impurities (economical & practical) energy use for transport & processing environmental impact of the processes level of demand for the recycled material
32
describe steps needed to recycle a metal
collect used items & transport to a recycling centre break up items & sort different metals melt metal & remove impurities solidify the metal in ingots (slabs of metal)
33
advantages & disadvantages of recycling
advantages: fewer quarries & mines less noise, traffic & air pollution fewer habitats destroyed metal ores conserved disadvantages: collection & transport of item needs fuel, workers, vehicles difficult to sort metals sorted metals might need to be transported
34
how are polymers disposed of?
incineration - releasing CO2 & toxic gas
35
most ores are
metal oxides so all extraction reaction reduce the metal
36
copper oxide + carbon →
copper + carbon dioxide
37
iron(III) oxide + carbon → Fe2O3(s) + 3CO(g) →
iron + carbon monoxide 2Fe(l) + 3CO2(g)
38
what are the stages of phytoextraction?
plants grown in soil contain low-grade ore (low % metal) plant absorbs metal ions & concentrate them in cells plants harvested & burnt ash contains metal compounds
39
what are the benefits of phytoextraction?
although slow, it reduces mining to obtain ore conserves high-grade ores reduces rock waste
40
describe the process of bioleaching & 1 advantage & disadvantages
bacteria can break down low-grade ores to form acidic solution containing copper ions the solution is called a leachate bioleaching does not need high temperatures but it: produces toxic substances, including sulfuric acid, which damage the environment
41
how are metal compounds produced by bioleaching processed?
iron more reactive than copper so iron displaces copper from the leachate iron + copper sulfate → iron(II) sulfate + copper or copper compounds can be dissolved & solution electrolysed to produce Cu
42
conditions that cause corrosion & product of corrosion
presence of water & oxygen hydrated metal oxide e.g. rusting iron + oxygen + water → hydrated iron(III) oxide
43
how can rusting & corrosion be prevented?
barrier to oxygen & water: painting coat in grease/oil sacrificial protection: galvanisation coat with more reactive metal so it corrodes instead of the protected metal
44
equation of Haber process
N2 + 3H2 ⇌ 2NH3
45
describe the steps in the Haber process
N2 (from air) & H2 (from natural gas) are pumped through pipes the pressure = 200atm temp. = 450°C iron catalyst mixture is cooled so that ammonia liquefies & removed unreacted nitrogen & hydrogen are recycled
46
how are nitrogen, phosphorus & potassium compounds important in agriculture?
in fertilisers to promote plant growth
47
how is ammonia used to make fertilisers?
it is oxidised to make nitric acid, which is the source of nitrate ions (NO3-) it can be neutralised by nitric acid to make the salt ammonium nitrate (NH4NO3) NH3 + HNO3 → NH4NO3 when this happens in aqueous solution, the equation is: ammonium hydroxide + nitric acid → ammonium nitrate + water NH4OH + HNO3 → NH4NO3 + H2O
48
what are the raw materials used in the industrial production of fertilisers?
raw materials mining potassium chloride & potassium sulfate = fertilisers phosphate rock cannot be used as a fertiliser because it is insoluble but it can be used to make fertilisers or lab synthesis
49
how does phosphate rock react with acids to form useful soluble compounds?
with nitric acid --> calcium nitrate & phosphoric acid --> ammonium phosphate with sulfuric acid --> single superphosphate (calcium sulphate & calcium phosphate) with phosphoric acid --> triple super phosphate (calcium phosphate)
50
how is sulfuric acid synthesised & what are the conditions of its reaction with ammonia?
sulfur + oxygen → sulfur dioxide sulfur dioxide + oxygen ⇌ sulfur trioxide (at 450°C) sulfur trioxide + water → sulfuric acid ammonia gas + sulfuric acid is continuous process that happens at 60°C, to form ammonium sulfate on a very large scale
51
ammonia sulfate in lab is made by reacting measured vol of ammonia solution & sulfuric acid solution - process?
1. 25cm^3 ammonia --> pipette --> conical flask 2. methyl orange indicator (yellow in alkaline ammonia) 3. add dilute sulfuric acid from burette until methyl orange = orange 4. record vol. sulfuric acid added 5. repeat without indicator
52
compare 2 methods of making ammonia sulfate (industrial vs lab)
see camera roll 21/10/24
53
desulfurisation equation
CaO + SO2 --> CaSO3
54
where did the atmosphere come from?
one theory: from intense volcanic activity, releasing gases which have lots of CO2, little or no O2, small amounts of ammonia & methane
55
how did oxygen concentration in the atmosphere increase over time?
photosynthesis by primitive plants & algae released oxygen, gradually building up over time
56
how did CO2 concentration in the atmosphere decrease over time?
formation of sedimentary rocks - CO2 dissolves in water to form carbonate compounds uptake by living organisms - organisms' food chains turned into fossil fuels billions of years ago, which contain carbon
57
how is the availability of potable water increased?
from freshwater: passing water through filter beds to remove insoluble particles sterilising water to kill microbes (chlorine, ozone, UV light)
58
describe desalinisation
= obtaining potable water from sea water distillation reverse osmosis: water put under high pressure & passed through partially permeable membrane
59
how is waste water treated?
screening & grit removal removes large particles sedimentation settles tiny particles from still water sewage sludge is digested anaerobically by bacteria effluent (liquid on top) is treated with aerobic bacteria to reduce volume of solid waste
60
enthalpy change of reaction =
= energy required to break bonds - energy required to form bonds = break - make

BMSAT (4 decks)

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