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paper 2 Flashcards

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1
Q

what is solubility normally expressed as

A

Solubility can be expressed in g per 100 g of solvent

for example 10g of salt can dissolve (before it gets saturated) in 100g of water which means the solubility is 10g/100g

if something is given not out of 100g then it must be converted
eg 10g/50g = 20g/100g

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2
Q

what is solublility

A

Solubility is a measurement of how much of a substance (solute) will dissolve in a given volume of a liquid (solvent)

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3
Q

what do solubility curves represent

A

Solubility graphs or curves represent solubility in g per 100 g of solvent with different temperature

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4
Q

what does above the solubility line mean

A

above the line means the solute will no longer dissolve

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5
Q

what does the solubility line mean

A

the solution is saturated

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6
Q

what does below the solubility line mean

A

the solute will dissolve

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7
Q

1.7C practical - investigate the solubility of a solid in water at a specific temperature

A
  1. set a water bath to a specific temperature (eg 50c)
  2. measure out 100g of water into a beaker
  3. place the beaker in the water bath
  4. add a thermometer to the beaker and once it has reached the same temperature as the water bath
  5. add a known mass of solid and stir until it has dissolved
  6. keep adding known masses in increments until not more dissolves
  7. write down what mass of solid that was added before solution got saturated
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8
Q

definition of a metallic bond

A

the electrostatic force of attraction between the delocalised free moving electrons and the positive metal ions

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9
Q

what is the strength of the attraction in a metallic bond determined by

A

the charge of the metal ions and by how many electrons there are

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10
Q

why do metals have a high boiling point and melting point

A

the electrostatic forces of attraction are very strong meaning it takes lots of energy to overcome giving them high melting and boiling points

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11
Q

what is a metallic bond

A

a group of metal atoms all donate their outer shell electrons into a delocalised sea of electrons (which can move freely throughout the structure) which then forms positive metal ions

the negatively charged sea of electrons attracts the positively charged ions bonding the metals

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12
Q

why do metals conduct so well

A

have a large sea of delocalised electrons that are free to move and conduct

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13
Q

why are metals malleable

A

when a force is applied instead of breaking or shattering, the ions can slide over each other as they are arranged in uniform layers

if any gaps are made in the structure when the force is applied, the delocalised electrons will move and fill in the gaps and therefore retain the structure and keep the properties

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14
Q

how to represent a metal lattice by a 2D diagram

A

large regular arrangement of circles with + inside then much smaller circles in the gaps between them with -

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15
Q

why do covalent compounds not conduct

A

electricity is the flow of charged particles and in covalent structures there are no freely moveble charged particles to carry current

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16
Q

why do ionic compounds only conduct when molten or in an aqueous solution

A

They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to move but when molten or in solution the particles become free to move as the lattice is broken down.

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17
Q

what is a cation

A

positively charged ion

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18
Q

what is a anion

A

negatively charged ion

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19
Q

moles equation in a liquid

A

moles = volume x concentration

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20
Q

moles in a gas equation

A

moles = volume / 24(decimeters)

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21
Q

electrolysis of molten compounds

A

when ionic compounds are melted into a molten state they can conduct electricity as they split into each ion
when the compound has undergo electrolysis they produce their corresponding element
positively charged ions (cations) move to cathode as it is negatively charged and at cathode they gain electrons to replace electrons lost when bonding making them back into element as they are no longer charged -> product will always be metal
negatively charged ions (anions) move to anode as it is positively charged and at anode they lose electrons to get rid of excess electrons gained when bonding turning back into element as uncharged -> product will always be non metal

for Lead(II) bromide
heat until molten
add in electrodes connected to circuit
lead ions go to cathode where they gain 2 electrons to form lead
bromide ions go to anode where they lose 1 electron each to form Br2 gas

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22
Q

ionic half equation for molten lead(II) bromide

A

at cathode:
Pb2+ + 2e- -> Pb which is reduction

at anode:
2Br- -> Br2 + 2e- which is oxidation

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23
Q

ionic half equation for aqueous sodium chloride

A

at cathode:
2H+ + 2e- -> H2 which is reduction

at anode:
2Cl- -> Cl2 + 2e- which is oxidation

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24
Q

ionic half equation for aqueous dilute sulfuric acid

A

at cathode:
2H+ + 2e- -> H2 which is reduction

at anode:
4OH- -> O2 + 4H2O + 4e- which is oxidation

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25
ionic half equation for aqueous copper(II) sulfate
at cathode: Cu2+ + 2e- -> Cu which is reduction at anode: 4OH- -> O2 + 2H2O + 4e- which is oxidation
26
practical: investigate the electrolysis of aqueous solutions
add aqueous solution to beaker add electrodes into beaker and ensure the tips don't touch add two inverted test tubes over electrodes to collect any gases produced connect electrodes to circuit with dc current make observations at each electrode test any gases collected
27
rules for determining product formed at cathode in aqueous electrolysis
either will be metal or hydrogen gas will be metal if the metal is less reactive than hydrogen eg copper will be hydrogen produces if metal is more reactive eg sodium
28
rules for determining product formed at anode in aqueous electrolysis
if the compound contains a halide ion (Cl- Br-) then halide ion is discharged compounds containing other negatively charged ions ( NO3 - SO4 2- CO3 2-) then the OH- ion from water is discharged forming 4OH- -> O2 + 4H2O + 4e- and releasing oxygen gas as O2
29
what happens to the reactivity as you go down group one
increases because as we go down the group each element has one more outer shell meaning the distance between the outer most shell and the nucleus increases. this decreases the electrostatic force of attraction meaning its easier to lose the one electron as less energy is required group one elements only need to lose one electron to form a complete outer shell
30
why does the reactivity decrease when you go down the halogen group
as you go down the group the amount mass of the halogens increase and so does the number of electron shells halogens form negative ions (they gain an electron) the distance from the nuclei (positive) to the outer shell increases which means there is a smaller force of attraction so it is harder to gain an electron
31
where are metals extracted from
from ores found in the Earth’s crust
32
what are unreactive metals found as
often found as the uncombined element as they do not react easily so they don't combine with other things
33
what is an ore
a naturally occurring rock which contains metals or metal compounds (eg iron oxide) in sufficient amounts to make them worthwhile extracting them
34
how is the method of extraction of a metal from a ore related to its reactivity
a more reactive metal can displace a less reactive metal the metals (aluminium) more reactive than carbon cannot be displaced by carbon so they need to be displaced by electrolysis metals (iron) less reactive then carbon can be displaced by carbon so they can be extracted by carbon extraction silver and gold are unreactive so they don't react with oxygen or anything else to form compounds which means they exist by themselves and therefore don't need to be extracted
35
what are the uses of aluminium
aeroplane bodies - very strong and low density (so it doesn't weigh a lot) power cables - good electrical conductor food cans - non-toxic, resistant to corrosion and acidic food window frames - resistant to corrosion
36
what are the uses of copper
wires - great electrical conductor cooking pans - great heat conductor water pipes - unreactive and malleable
37
what are the uses of iron
making steel - steel is more useful
38
what are the uses of low-carbon steel
ships, cars, bridges - strong and malleable
39
what are the uses of high-carbon steel
tools (knives + screwdrivers) - strong and less malleable so won't change shape
40
what are the uses of stainless steel
cutlery, kitchen sinks - Cr forms oxide layers that is resistant to corrosion and stays shiny and clean
41
what does malleable mean
can be hammered into different shapes without cracking
42
what does ductile mean
can be drawn into wires
43
what is low-carbon steel made of
Fe + 0.1% C
44
what is high-carbon steel made of
Fe + 1% C
45
what is stainless steel made of
Fe + 1% C + 10% Cr
46
what is an alloy
a mixture of a metal and one or more elements, usually other metals or carbon
47
why are alloys harder than pure metals
the different-sized atoms/ions which distorts the regular arrangement therefore preventing the layers of metal ions from sliding over each other making it harder
48
things to comment on for electrolysis
large amounts of electricity are required making it very expensive
49
things to comment on for carbon extraction
much cheaper than electrolysis and is a source of heat as well
50
describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an acid and alkali
acid + alkali (soluble base) --> salt + water titration 1. the alkali and a few drops of indicator to a conical flask 2. add acid to a burette and note the starting volume 3. slowly add the acid to the alkali until the indicator changes colour 4. record the final volume of acid and calculate the total volume of acid added 5. get the same amount of alkali without the indicator and add the total volume of acid added to the other one (this creates pure crystals without the indicator in them) 5. heat the salt solution until crystals just start to appear 6. as soon as they appear, remove from heat 7. leave evaporating basin in a warm place in the sun for a few days to allow water to evaporate
51
describe an experiment to prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants
soluble salt 1(aq) + soluble salt 2(aq) --> insoluble salt(s) + soluble salt 3(aq) 1. mix the 2 soluble salts together in water using a stirring rod 2. filter the solution using a funnel and filter paper 3. pour distilled water through the filter paper to wash the insoluble salt 4. place the insoluble salt in a warm dry sunny place to dry the salt
52
practical: prepare a sample of pure, dry lead(II) sulfate
insoluble salt from 2 soluble reactants 1. Measure out 25 cm3 of 0.5 mol dm3 lead(II)nitrate solution and add it to a small beaker 2. Measure out 25 cm3 of 0.5 mol dm3 of potassium sulfate add it to the beaker and mix together using a stirring rod 3. Filter to remove precipitate from mixture 4. Wash filtrate with distilled water to remove traces of other solutions 5. leave in sunny warm place to dry
53
how to carry out an acid-alkali titration
Titrations are a method of analysing the concentration of solutions They can determine exactly how much alkali is needed to neutralise a quantity of acid – and vice versa Use the pipette and pipette filler and place exactly 25 cm3 known acid solution into the conical flask fill the burette with an alkali Place the conical flask on a white tile so the tip of the burette is inside the flask Add a few drops of phenolphthalein indicator to the solution in the conical flask Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus Now repeat the titration with a fresh batch of acid As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour Record the volume to the nearest 0.05 cm3 Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy
54
what is bond breaking
a endothermic process as it takes in energy to break down the bonds
55
what is bond making
an exothermic process as energy is released when new bonds are formed
56
how to use bond energies to calculate the enthalpy change during a chemical reaction
calculate the energy energy taken in from the reactants calculate the energy released from making the bonds enthalpy change = energy taken in - energy released
57
how to draw an energy level diagram
energy on the y axis progress of reaction on the x axis for an endothermic: reactants have less energy than products as energy is taken in so reactants line is below products. Arrow is pointing upwards for an exothermic: reactants have more energy than products as energy is given out. reactants line is above products and arrow points down
58
draw and explain reaction profile diagrams showing ΔH and activation energy
similar to energy level diagrams except instead of an arrow there is bump as they show how the energy changes as the reaction progresses The difference in height between the energy of reactants and products represents the overall enthalpy change of a reaction The initial increase in energy, from the reactants to the peak of the curve, represents the activation energy, Ea, required to start the reaction The greater the initial rise then the more energy that is required to get the reaction going e.g., more heat needed
59
how can a reversible reaction reach dynamic equilibrium
in a sealed container where no moles can enter or escape
60
characteristics of a reaction at dynamic equilibrium
forward and reverse reactions occur at the same rate the concentrations of reactants and products remain constant
61
does a catalyst affect the position of the equilibrium in a reversible reaction
NO because the catalyst increases the rate of both the forward and backward reactions by the same amount so the whole thing just happens faster does not prioritise one side catalyst does speed up rate at which equilibrium is reached
62
affect on changing temperature on position of equilibrium in reversible reaction
increasing temp shifts equilibrium in the direction of the endothermic reaction to use up excess heat decreasing temp shifts equilibrium in the direction of the exothermic reaction to produce more heat
63
affect on changing pressure on position of equilibrium in reversible reaction
increasing pressure shifts equilibrium in the direction that produces fewer moles of gas decreasing pressure shifts equilibrium in the direction that produces more moles of gas
64
what functional group is alcohols
-OH
65
how can ethanol be oxidized
burning in air or oxygen (complete combustion) forms water and CO2 (microbial oxidation)bacteria in air use oxygen to oxidise ethanol forming ethanoic acid and water heating with potassium dichromate(VI) (oxidising agent) in dilute sulfuric acid to form ethanoic acid and water and turns orange to green
66
manufacturing of ethanol - fermentation
add sugar/starch to water with yeast ferment the mixture at between 30-40c (to prevent the enzymes from denaturing) without oxygen for a few days yeast contains the enzymes that break down glucose into ethanol and CO2 when they respire anaerobically then the ethanol and water are separated by fractional distillation the yeast then denatures when the alcohol reaches 15% so the process has got to be constantly repeated (why fermentation is a batch process)
67
manufacturing of ethanol - hydration of ethene
hydrocarbons cracked to form ethene ethene and steam are passed over phosphoric acid (catalyst) requires: 300'c temp 60-70 atm pressure concentrated phosphoric acid catalyst
68
reasons for fermentation
carried out at a low temperature (30-40) does not require oxygen sugar is renewable does not pollute the environment
69
catalyst required to crack alkanes
silica or aluminum oxide
70
catalyst used when hydrating ethene
phosphoric acid
71
functional group of carboxylic acids
-COOH with a double bond between the C and first O and then the OH is also bonded to the C
72
reactions of carboxylic acids(aq) with metals
carboxylic acid + metal -> salt + hydrogen same as a regular acid reacting salt formed ends -anoate eg, ethanoic acid forms ethanoate
73
reactions of carboxylic acids(aq) with metal carbonates
carboxylic acid + metal carbonate -> salt + water + carbon dioxide salt formed ends -anoate
74
examples of carboxylic acids
vinegar which is an aqueous solution
75
functional group of esters
-COO- the first O is double bonded to the C and the other O is single bonded to the C
76
how is ethyl ethanoate formed
ester produced when ethanol and ethanoic acid react in the presence of an acid catalyst
77
displayed formula of ethyl ethonoate
, H H O H I I II I H-C-C-O-C-C-H I I I H H H
78
structural formula of ethyl ethanoate
CH3 CH2 CO2 CH3
79
how is an ester formed
carboxylic acid + alcohol -> ester + water need acid as catalyst usually sulphuric acid the ester is formed by combining the carboxylic acid and alcohol however the acid loses OH and the alcohol loses H which is where the water comes from
80
catalyst used for esters
any acid usually sulphuric
81
how to name an ester
first word is the prefix from the alcohol and ends in -yl second word is the prefix from the carboxylic acid and ends in -oate Eg, methanol + ethanoic acid -> methyl ethanoate + water
82
properties of esters
volatile compounds distinctive smells
83
uses of esters
food flavourings perfumes
84
practical: prepare a sample of an ester such as ethyl ethanoate
A mixture of ethanoic acid, ethanol and concentrated sulfuric acid is gently heated by either a water bath or an electric heater (ethanol is flammable, so a Bunsen can’t be used!) The ester is then distilled off as soon as it is formed and collected in a separate beaker by condensation As esters have low boiling points (they are volatile), they are the first to evaporate from the reaction mixture. Removing them from the mixture by distillation prevents the reverse reaction from occurring
85
how is a condensation polymer formed
a dicarboxylic acid and a diol react producing a polyester and water condensation polymers are formed from two different monomers joining and a water is lost per linkage
86
difference between addition and condensation polymers
addition forms only the polymer molecule condensation forms the polymer molecule and one water molecule per linkage addition are only formed by alkenes repeating condensation are formed from a diol and dicarboxylic acid alternating
87
what is a dicarboxylic acid
a regular carboxylic acid except the functional group is on both ends O O II II H-O-C-C-O-H
88
What is a diol
an alcohol with the functional group on both ends H H I I H-O-C-C-O-H I I H H
89
ethanedioic acid + ethanediol
monomers: O O II II n H-O-C-C-O-H + n H-O-CH2-CH2-O-H Polymer: O O II II -(-C-C-O-CH2-CH2-O-)- + 2n H2O

Chemistry (6 decks)

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