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OCR Gateway A GCSE Chemistry > C4 - Predicting and Identifying Reactions and Products > Flashcards

C4 - Predicting and Identifying Reactions and Products Flashcards

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1
Q

where are group 1 elements found

A
  • placed in the vertical column on far left of the periodic table
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2
Q

what are group 1 elements known as and why

A
  • Alkali metals
    > because they react with water to produce an alkaline solution (metal hydroxide) + hydrogen gas
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3
Q

what properties do group 1 metals have

A
  • shiny when freshly cut
  • good conductors of heat
  • solid at room temp but are soft enough to cut with knife
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4
Q

what are the general trend going down group 1

A
  • density increases
  • melting point decreases
  • softer metals
  • reactivity increases
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5
Q

what do group 1 meals react with

A
  • water
  • oxygen
  • acids
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6
Q

what does the reaction of group 1 metals with water produce

A
  • metal hydroxide + hydrogen
    > e.g. sodium reacts with water to form sodium hydroxide + hydrogen
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7
Q

why are group 1 metals stored in oil

A
  • because they react rapidly with oxygen in air and water
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8
Q

what does the reaction of group 1 alkali metals with acids produce

A
  • salt + hydrogen gas
    > these reactions are more violent than the ones with water - dangerous to do in school lab
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9
Q

what is the trend of reactivity down group 1 metals and why

A
  • elements get more reactive as you go down the group
    > because the outer electron becomes further away from the positive nucleus and so the attraction between them becomes weaker
    > this means that the attractive force is more easily broken, so less energy is required to remove the electron
  • the easier it is for a group 1 atom to lose its outer shell electron the more reactive the element is
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10
Q

what is the general ionic equation for group 1 elements

A

M —-> M+ + e-
(loses electron)

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11
Q

what charge do group 1 metals carry

A

+1
> they lose on electron to obtain a full outer shell and a stable electron configuration

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12
Q

why do elements in the same group have similar chemical properties

A
  • because they have a similar electron configuration (same number of outer shell electrons)
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13
Q

what are group 7 elements also known as

A
  • halogens
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14
Q

what some properties of group 7 elements

A
  • non metals
  • brittle in solid state
  • poor conductors of electricity
  • exist as diatomic molecules
    > with weak intermolecular forces
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15
Q

what is the colour + state of fluorine at room temperature

A
  • pale yellow gas
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16
Q

what is the colour + state of chlorine at room temperature

A
  • green gas
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17
Q

what is the colour + state of bromine at room temperature

A
  • orange-brown liquid
    > easily vaporises
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18
Q

what is the colour + state of iodine at room temperature

A
  • shiny grey-black crystalline solid
    > sublimes to form purple vapour
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19
Q

describe the trend in boiling point down group 7

A
  • boiling points increase
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20
Q

describe the trend in density down group 7

A
  • density increases
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21
Q

what do group 7 elements react with

A
  • halogens react with metals to form salts
    > the reactions are typically vigorous with group 1 metals, especially if the metal is heated first
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22
Q

what is the trend of reactivity down group 7

A
  • reactivity decreases
    > because the outer shell becomes further away from the positive nucleus and so the attraction becomes weaker
    > it’s harder for the electron to get attracted to the outer shell so reactivity decreases
  • the easier it is for a halogen atom to gain an electron the more reactive the element is
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23
Q

what is the general ionic equation for group 7 elements

A

X2 + 2e- —-> 2X-
(gains electron)

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24
Q

what charge do halide ions carry

A

-1
> they gain one electron to complete a full outer shell to obtain a stable electron configuration

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25
Q

what is a halide

A
  • a compound containing a group 7 elements + one other element (usually hydrogen or a metal)
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26
Q

apart from metals what else can halogens react with

A
  • metal halides in solutions
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27
Q

what are displacement reactions in halogens

A
  • a halogen will displace a less reactive halogen from its halide ions in solution
    e.g. chlorine displaces bromine from bromides and iodine from iodides
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28
Q

why are halogen displacement reactions carried out

A
  • they are used to confirm the order of reactivity of chlorine, bromine and iodine
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29
Q

how can you carry out halogen displacement reactions

A
  • wear eye protection
  • place a small volume of halide salt (potassium chloride/bromide/iodide) solution in a spotting tile
  • add a few drops of halogen solution (chlorine/bromine/iodine water)
  • note down the observations - if you see a colour change the reaction has occurred
  • repeat for different combos of halide salt + halogen
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30
Q

what colour are solutions of chlorine, bromine and iodine

A
  • chlorine water = colourless
  • bromine water = orange
  • iodine = brown
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31
Q

what do you observe when chlorine is added to each of the halide salt solutions

A
  • potassium chloride = no reaction
  • potassium bromide = orange
  • potassium iodide = brown
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32
Q

what do you observe when bromine is added to potassium iodide

A
  • brown colour
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33
Q

what are the half equations for the displacement reaction when: chlorine displaces bromine from bromide ions

A

Cl2 + 2e- —-> 2Cl- reduction
2Br- —-> Br2 + 2e- oxidation
- combine to make ionic equation
Cl2 + 2Br- —-> 2Cl- + Br2

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34
Q

what are group 0 elements known as

A
  • noble gases
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35
Q

why are noble gases called what they are

A
  • because they are so unreactive + take part in very few chemical reactions due to having a full outer shell
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36
Q

what state are group 0 elements

A
  • gas at room temp
  • non-metals
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37
Q

why are noble gases so unreactive

A
  • they have a complete outer shell
    > they don’t have the tendency to lose/gain electrons to form ions in reactions or to share electrons to form molecules in reactions
    > as a result they are very unreactive
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38
Q

the noble gases are monatomic, explain what that means

A
  • they exist as single atoms with very weak forces of attraction between them
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39
Q

why do noble gases have low boiling points

A
  • because they have weak intermolecular forces between the atoms which require little energy to overcome
    > this is why they are all gases at room temp
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40
Q

what trends going down noble gases are present

A
  • attractive forces between atoms get stronger
  • boiling point increases (as atoms become larger)
  • density increases
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41
Q

why do noble gases have very low densities

A
  • because their atoms are far apart in the gas state, so there is very little mass in a given volume
    > as you go down group 0 the density increases
42
Q

where are transition metals in the periodic table

A
  • between groups 2 + 3
43
Q

what are the properties of transition metals

A
  • metals
  • shiny when freshly cut
  • good conductors of electricity
  • strong
  • malleable (can be bent into shape)
44
Q

in comparison to group 2, the transition metals are:

A
  • stronger + harder
  • have higher densities
  • have higher melting points (except mercury which is liquid at room temp)
45
Q

what are the chemical properties of transition metals

A
  • they are less reactive than alkali metals
    > they react slowly, if at all
46
Q

transition metals: what happens when iron reacts slowly with water / oxygen

A
  • produce hydrated iron (III) oxide = rust
47
Q

do gold, platinum and iridium react with water/oxyegn

A

no

48
Q

transition metals produce _____ ionic compounds

A
  • coloured
49
Q

unlike alkali metals which can only form +1 ion charges what can transition metals do

A
  • they can form more than one type of ion
    > as they have complex electron configuration
    > e.g. iron can be Fe2+ or Fe3+
50
Q

transition metals are often good ____

A
  • catalysts
    > because of their ability to form different ions as they have complex electron configuration
51
Q

metals form positive ions in reactions, the more easily this happens _____

A
  • the more reactive the metal is
52
Q

when can metals react with water / dilute acids

A
  • if the metal is more reactive than hydrogen
53
Q

metals react with water to produce ____

A
  • metal + water —> metal hydroxide +hydrogen
54
Q

metals react with acids to produce ____

A
  • metal + acid —> salt + hydrogen
55
Q

what can be used to put metals in order of their reactivity + why

A
  • reactions of metals with water/dilute hydrochloric acid
    > produces hydrogen
    > the more reactive the metal, the greater the rate of hydrogen production
    > so more vigorous bubbling
    > so you measure the rate at which hydrogen gas is produced
56
Q

when carrying out metal + water/ dilute hydrochloric acid reactions what mustn’t you do

A
  • boil the water/acid because it would bubble when boiled, so you wouldn’t be able to tell if the bubbles were due to a reaction
    > it would also be unsafe to boil the acid as it could splatter everywhere
57
Q

what are metal displacement reaction

A
  • a more reactive metal can displace a less reactive metal from solutions of it’s compounds
    > e.g. copper is more reactive than silver so it can displace silver from silver nitrate solution
58
Q

displacement reactions are an example of ____

A
  • redox reactions
    > e.g. Cu(s) + 2AgNO3(aq) —-> Cu(NO3)2(aq) + 2Ag(s)
    Cu(s) —–> Cu2+(aq) + 2e- (oxidation)
    Ag+(aq) + e- —–> Ag(s) (reduction)
59
Q

how can you carry out metal displacement reactions

A
  • place small volume of the metal salt solution in a spotting tile
  • add a piece of the metal
  • note your observations
  • repeat with other combos of metal + metal salt
60
Q

metals in groups 1 + 2 are more _____

A
  • reactive than transition metals and other metals
61
Q

how can you test for carbon dioxide

A
  • using limewater
    > limewater = calcium hydroxide solution
  • limewater turns cloudy when carbon dioxide is bubbled through it
    > because calcium hydroxide + carbon dioxide = water + white precipitate of calcium carbonate
62
Q

how can you test for chlorine

A
  • hold a piece of damp blue litmus paper over the substance
  • if chlorine is present, it will bleach the paper white
    > it will be red at first for a bit because chlorine solution is acidic
63
Q

how can you test for hydrogen

A
  • place a lighted splint near the mouth of the container of gas
  • if hydrogen is present a squeaky pop will be produced
    > because hydrogen burns with oxygen in air to form water
64
Q

how can you test for oxygen

A
  • place a glowing splint near the mouth of the container of gas
  • if oxygen is present, the splint should relight
65
Q

what can you use to test for cations

A
  • flame tests
  • hydroxide precipitate tests
66
Q

what are flame tests used to detect

A
  • metal ions
  • the different metal ions give off different colours of light
67
Q

why do metal ions give off different flame colours

A
  • when metal ions are heated, energy is transferred to their electrons
    > this allows the electrons to momentarily jump up to a higher energy shell, before falling back to their normal position
  • when they fall back they release energy to the surroundings as radiation, which you see as light
    > different metal ions produce different colours of light
68
Q

how can you carry out a flame test

A
  1. collect equipment: nichrome wire loop, Bunsen burner, hydrochloric acid, samples to test, distilled water
  2. clean nichrome wire loop by dipping into hydrochloric acid then rinsing with distilled water - if clean, there will be no change in colour of Bunsen burner flame when you hold the loop in it
  3. dip the clean loop into test power / solution
  4. use a handle to hold the loop in the edge of a roaring blue flame
  5. record the flame colour
  6. clean the wire loop and repeat with other substances
69
Q

why is a nichrome wire loop used to carry out flame tests

A
  • because it’s inert
    > so won’t react with the test substance and doesn’t emit a colour of its own in the flame
70
Q

what colour flame does lithium ion produce

A

crimson red

71
Q

what colour flame does sodium ion produce

A

yellow
(sodium just seems yellow)

72
Q

what colour flame does potassium ion produce

A

lilac
(potassium sounds like a sweet flower which is lilac - also p for purple but it’s actually lilac)

73
Q

what colour flame does calcium ion produce

A

orange-red
(bones surrounded by orange + red like blood??)

74
Q

what colour flame does copper ion produce

A

green-blue
(copper rusts to this colour)

75
Q

what is another way to test for metal cations

A
  • hydroxide precipitate tests
76
Q

what reagent is used for hydroxide precipitate tests

A
  • sodium hydroxide solution
    > it’s water soluble so you can see the precipitate form
    > group 1 metal hydroxides are soluble in water but most other metal hydroxides are insoluble
77
Q

how do you carry out hydroxide precipitate tests

A
  • add a drop of sodium hydroxide solution to a solution containing the metal ions and note the colours of the hydroxide precipitate formed
78
Q

what is the colour precipitate of calcium ions when reacted with sodium hydroxide + give ionic equation

A
  • white
    Ca2+(aq) + 2OH- (aq) —-> Ca(OH)2 (s)
79
Q

what is the colour precipitate of zinc ions when reacted with sodium hydroxide + give ionic equation

A
  • white at first but turns colourless in excess of sodium hydroxide (NaOH)
    Zn2+(aq) + 2OH- (aq) —-> Zn(OH)2 (s)
80
Q

what is the colour precipitate of iron (II) ions when reacted with sodium hydroxide + give ionic equation

A
  • green
    Fe2+(aq) + 2OH-(aq) —-> Fe(OH)2 (s)
81
Q

what is the colour precipitate of iron (III) ions when reacted with sodium hydroxide + give ionic equation

A
  • brown
    Fe3+(aq) + 3OH-(aq) —-> Fe(OH)3 (s)
82
Q

what is the colour precipitate of copper (II) ions when reacted with sodium hydroxide + give ionic equation

A
  • blue
    Cu2+(aq) + 2OH- —-> Cu(OH)2 (s)
83
Q

how can you distinguish between calcium hydroxide and zinc hydroxide

A
  • as both form white precipitates
    > add an excess of sodium hydroxide solution as zinc hydroxide dissolves to form a colourless solution but calcium hydroxide doesn’t dissolve
84
Q

what are the different anions you need to test for

A
  • carbonate ions
  • sulfate ions
  • halide ions
85
Q

how can you detect sulfate ions

A
  • barium ions react with sulfate ions to produce white, insoluble barium sulfate
    > add a few drops of dilute hydrochloric acid
    > add a few drops of barium chloride solution
    > if sulfate ions are present, a white precipitate forms
86
Q

how can you detect carbonate ions

A
  • hydrogen ions from dilute acids react with carbonate ions to produce carbon dioxide
    + water
    > add a few drops of dilute hydrochloric acid
    > if carbonate ions are present, bubble of gas will be produced
    > to confirm if the gas is carbon dioxide, bubble it through limewater
87
Q

how do you detect halide ions

A
  • add a few drops of dilute nitric acid
  • add a few drops of silver nitrate solution
  • if one of the halide ions are present, a coloured precipitate forms
88
Q

what colour precipitate does silver chloride produce

A

white

89
Q

what colour precipitate does silver bromide produce

A

cream

90
Q

what colour precipitates do silver iodide produce

A

yellow

91
Q

why is acid added in sulfate + halide ions tests

A
  • to remove carbon impurities as they can often result in false positive result
92
Q

what is the ionic equation for reaction of sulfate ions with barium chloride

A

Ba2+(aq) + SO42-(aq) —-> BaSO4(s)

93
Q

what is the ionic equation for the reaction of carbonate ions with acid

A

CO32-(aq) + 2H+(aq) —-> CO2(g) + H2O(l)

94
Q

what are instrumental methods of analysis

A
  • instrumental analysis relies on machines to carry out analysis of a substance
95
Q

what are some advantages of instrumental analysis

A
  • sensitivity - can analyse very small amounts of substances - useful if substance is expensive or difficult to obtain
  • accuracy - instruments are very accurate + can be calibrated using internationally accepted standards
  • speed - instruments can carry out analysis quickly + can run all the time
96
Q

what are some disadvantages of instrumental analysis

A
  • costly
  • needs highly skilled operators
  • large equipment
  • needs setting up
97
Q

how can you interpret gas chromatograms

A
  • each peak represents a substance present in the mixture
  • areas under each peak show the relative amounts of each substance in the mixture
  • the retention time (time taken for a substance to travel through the chromatography column) is different for different substances
98
Q

what does a mass spectrometer measure

A
  • the masses of atoms + molecules to help work out the structure of unknown substances
99
Q

how does mass spectrometry work

A
  • samples are fired through a machine
  • samples are ionised to form molecular ions (always positive)
  • these ions can break to form fragments which the machine separate and detect
100
Q
A

OCR Gateway A GCSE Chemistry (7 decks)

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