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A level Chemistry > Chapter 8 - Reactivity trends > Flashcards

Chapter 8 - Reactivity trends Flashcards

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1
Q

outer shell configuration of G2 elements?

A

s (^2)

- are in s block

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2
Q

ions formed by G2 elements?

A

2+ ions

- loss of S(^2) electrons in in redox reactons

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3
Q

G2: properties from Magnesium to Barium (not Bryllium)?

A
  • High MP & BP
  • low densities
  • form colourless compounds
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4
Q

which G2 element has a lower BP than expected and why?

A

Mg bc of the way atoms pack toegther when metallically bonded

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5
Q

Trend in reducing ability of G2 elements (1st and 2nd IE)

A
  • ⬇ G electrons are lost more readily
  • NC ⬆, but AR & S also ⬆
  • overall, outer 2e-s attracted less strongly
  • ⬇ G, elements become stronger reducing agents
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6
Q

the type of bonding in G2 is?`

A

GIANT METALLIC BONDING`

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7
Q

why does MP decrease down G2 from Ca?

A
  • as go down group
  • all of G2 ‘lose’ the 2 outer e- to the sea of delocalised e-s
  • AR and S inc
  • Change in charge density
  • electrostatic attraction from + ions for delocalised e- decreases, so less energy needed to break metallic bond
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8
Q

G2: change in charge density?

A

bc the AR inc and the charge is the same, the charge is spread over a larger ‘volume’

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9
Q

reactions of G2 with Oxygen equations (2)

A
  • Ca + O2 -> 2CaO(s)
  • Sr + O2 -> SrO(s)
  • ONLY METALOXIDE IS FORMED!!
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10
Q

Metals are always ___ ions?

A

+

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11
Q

G2 oxides and hydroxides are?

A

bases

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12
Q

G2 oxides and hydroxies are neutralised by acids to form ?

A

salt + water

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13
Q

G2 oxide + acid equation

A

CaO + HCl -> CaCl2 + H20

- salt and hydrogen are formed

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14
Q

G2 elements react with water to form?

A

metal hydroxides with a pH between 10 -12

  • mg hydroxide = pH 9
  • CaOH2 = 10/11
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15
Q

CaO and water reaction?

A

CaO +H20 -> Ca(OH)2

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16
Q

G2 hydroxides dissolve in water to form ?

A

alkaline solutions, with a pH between 10-12

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17
Q

solubility ____ down G2

A

increases (of hydoxides)

- meaning pH increases, become more alkali

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18
Q

solubility of hydroxide equation>?

A

Mg(OH)2 -> Mg 2+ + 2OH -

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19
Q

general equation for G2 reactions?

A

M - 2e(^-) -> M 2+
Ca - e- -> Ca2+
- is like the 1st and 2nd IE

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20
Q

trends down G2 are:

A
  • Reactivity inc
  • AR inc
  • IE dec
  • Solubility of hydroxides inc
  • pH of hydroxides increases
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21
Q

physical properties of the halogens:

A
  • Chlorine - yellow/pale green gas at RTP
  • Br2 - dark orange liquid at RTP
  • I2 - grey solid at RTP
  • F2 - colourless gas at RTP
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22
Q

Why don’t we keep F or As in college?

A
  • F is v reactive, dangerous

- As - radioactive element

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23
Q

Bromine is used to test for?

A
  • alkenes
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24
Q

iodone is used to test for?

A

starch

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25
Q

Down G7, Mp ?

A

inc

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26
Q

electron arrangement of halogens ?

A

p5

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27
Q

TREND IN MP &BP DOWN G7 EXPLAINED?

A
  • down G , they increase
  • induced dipole forces between molecules, broken during M&B
  • Strength of these induced dipole inc down G as no. of e-s increases, more energy required to break them, higher Mp&BP
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28
Q

Colours of the Halogens - Chlorine?

A
  • in water: pale/ yellow

in cyclohexane: yellow

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29
Q

Colours of the Halogens - Bromine?

A
  • in water: orange

- in cyclohexane - darker orange

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30
Q

Colours of the Halogens - iodine?

A
  • in water: dark red/ brown

- in cyclohexane: purple layer

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31
Q

Colours of the Halogens - fluorine?

A
  • in water - colourless

- in cyclohexane - colourless

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32
Q

what do the colours show about the solubility of the halogens in the 2 solvents?

A
  • the darker colours in cyclohexane show the halogens dissolve better in cyclohexane
  • water is a polar solvent, water mols stick together due to strong H bonds
  • cyclohexane has no permanent dipole so can form induced dipoles with halogen
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33
Q

(GCSE) a more reactive halogen will ____ a less reactive halogen from a halide compound?

A

displace

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34
Q

when halogens react with a solution, the halide solution formed will be….

A
  • colourless but the halogen will be coloured
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35
Q

Chlorine, Bromine Ionic equation?

A

Cl2 + 2Br - -> 2CL - + Br2

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36
Q

use _____ ___ instead of displacement?

A

oxidising ability

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37
Q

explain the trend in reactivity down G7 in terms of oxidising ability?

A
  • halogens at top are the best oxidising agents
  • down G7, eventho NC ⬆, S ⬆, so AR⬆
  • = less attration between nucleus and outer shell electron
  • = more diff for nucelsut o attract the 1 e- needed
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38
Q

In an explaining trend in reactivity of G7 ques, always include

A
  • oxidising agents

- overall, down the group, halogens have less attractive force on the incoming electron

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39
Q

what is a disproportionation reaction?

A

the same element is both oxidised and reduced

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40
Q

halogens have ______ ____?

A

disproportionation reactios

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41
Q

reaction of chlorine and water?

A

Cl2 + H20 -> HCl + HClO

  • hydrochloric acid/ hydrogen chloride produced
  • and chloric acid hydrogen chlorate (I)
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42
Q

Benefit of adding chlorine to water?

A
  • hydrogen chlorate (I) is produced which will kill germs/b bacteria/ viruses
43
Q

suggest a risk of adding chlorine to water?

A
  • Cl2 in the envir forms chlorinated hydrocarbons with organic chemicals. These may cause cancer
44
Q

(Disproportionation) reaction of chlorine with sodium hydroxide solution

A

Cl2 (g) + 2NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O

  • Sodium Chlorate (I)
  • sodium chloride
45
Q

Chlorine and sodium hydroxide ionic equation?

A

Cl2 + 2OH -> Cl- + ClO- + H2O

46
Q

sodium chlorate use?

A
  • powerful oxidising agent that kills bacteria and acts as a bleach, removing colour
47
Q

overall the increase and decrease in Ox no. must be

A

equal

- use ox no when equations diff to balance

48
Q

colours of aqueous solutions of halide ions?

A
  • F- = colourless
  • Cl- = colourless
  • Br- = colourless
  • I- = colourless
  • a chemical test is needed to identify the halide ions
49
Q

testing for halides?

A

1 - add dilute nitric acid
2 - add silver nitrate
3 - add ammonia, dilute then conc to see if precipitate dissolves

50
Q

identifying chloride ion?

A
  • white precipitate forms - AgCl
  • Ag+ (aq) + Cl-(aq) -> AgCl(s)
  • dissolves in dilute ammonia
51
Q

identifying Bromide ions?

A
  • cream precipitate forms - AgBr

- dissolves in conc ammonia to form a colourless solution, not in dilute tho

52
Q

identifying Iodide ions?

A
  • yellow precipitate -AgI

- insoluble - doesn’t dissolve in both dilute & conc ammonia

53
Q

when doing a test for halides on foods?

A
  • ,make a SOLUTION by DISSOLVING food

- make clear by filtering

54
Q

Boiling as water purification?

A
  • is extremely effec in eliminating microbiological contaminants from the water
  • removes: microrganisms
  • doesn’t remove: heavy metals
    + = no cost involved, very effective in removing harmful organisms
  • = time consuming, smell and taste not improved
55
Q

distillation as water purification?

A
  • water is first heated to boiling, water vapour rises to a condenser where vapour is condensed, collected + stored. most contaminants remain behin din the liquid phase vessel
  • = organics with BP < 100 cannot be remove effec and can become conc in the product H20
  • requires large amounts of energy
56
Q

Filtration as water purification?

A
  • good for dealing with all types of water contaminants
    removes: bacteria, cysts, some will eliminate chemicals, heavy metals, pesticides, virsuses
  • don’t remov: depends on type
    + = usually light, portable, quick and cost effective
  • = filters will eventually need to be replaced, flow rate may be slow
57
Q

UV light as water purification?

A
  • great for neutralising microbiological contaminants such as bacteria, viruses
  • kills: microorganisms
  • DR: chemicals, heavy metals, sediments, debris
    + = small + lightweight
  • = won’t remove sediment, odours, debris
58
Q

Iodine crystals as water purification?

A
  • relatively convenient, comes in a no. of forms
    kills: bacteria, viruses
    + = light weight, easy to use
  • = 20-30 min delay b4 drinking, no safe for preg women, some tablets leave a strong after taste
59
Q

purification tablets/ halogens as water purification?

A
  • use chemicals to kill microbiological contaminants. The most comn tablets are made from CL, AG, Cl dioxide, iodine was BANNED
  • kill: microorganisms
  • DR: chemicals, pesticides, heavy metals, sediments
    + = small, lightweight, cheap, cost effective
  • = usually have foul taste, waiting time, still drink the chemicals and addetives
60
Q

to avoid false positives?

A

the sequence of the tests should be perormed in is carbonate, sulfate, then halide. (Barium Carbonate and silver sulfate are both insoluble)

61
Q

test for carbonates?

A
  • add 1moldm-3 nitric acid
  • cloudy
  • salt + water + carbon dioxide formed
62
Q

tests for sulphates?

A
  • dilute nitric acid
  • add barium chloride solution
  • white precipitate of BaSO4 (s)
    (Ba2+ + SO42-)
63
Q

why do we test for carbonates 1st?

A
  • CO2 + H20 -> H2CO3
    carbon dioxide from air, reversible reaction
  • thfr, any sol may contain carbonate ions
  • if carbonate present, false +
  • nitric acid removes dissolved CO2 and carbonate ions
64
Q

TEST FOR AMMONIUM ION: CATION?

A
  • add 2cm3 of 1moldm-3 NaOH to a spatula of solid ammonium compound
  • gently warm
  • gas released turns red litmus paper blue
    NH4+ +OH- -> NH3(g) + H2O - ammonia = alkali
65
Q

qualitative test?

A
  • presence not conc

- observed changes

66
Q

which electrons are lost when G2 metals react?

A

outer shell s2 electrons to gain a noble gas configuration

67
Q

why are G2 elements reducing agents?

A

they r very easily oxidised

68
Q

G2 metal and water equation?

A

Mg +2H2O -> H2 + Mg(OH)2

  • Mg so v slow reaction
  • metal hydroxide and hydrogen gas formed
69
Q

why does the pH of solutions increas ⬇ G2?

A
  • ⬇ G, oxides react more readily with water

- giving more hydroxide ions in solution

70
Q

what does the solubiity of g2 hydroxides do ⬇ G

A

increases

71
Q

use of calcium hydroxide?

A
  • neutralisation
  • used in agriculture to neutalise acidic salts
  • Ca is used as more soluble than Mg hydroxide, more alkaline, saves farmer money
  • calcium hydroxide + nitric acid -> cal nitrate + water
72
Q

use of Mg hydrox and calcium carbonate?

A
  • as ‘antacids’
  • treating indigestion
  • alkali’s are corrosive, Mg hydrox is milder alkali so safer to take into our bodies, less soluble so doesn’t dissolve and go into blood - needed in stomach
  • Mag hydrox + hydrochloric acid -> mag chloride + water
73
Q

why is G2 know as the alkali earth metals?

A
  • react with water to form alkali solutions

- earth - old term that comes from metals that aren’t very soluble and are heat resistant

74
Q

RULE - nitrates?

A
  • all nitrates and G1 compounds tend to be soluble
75
Q

the more soluble the hydroxide, the less…

A

precipitate will form

76
Q

G2 - what increases ⬇ G

A
  • AR
  • A no
  • Solubility
  • pH of hydroxides
  • Reactivity/ reducing ability
  • Density
77
Q

G2 - what decreases ⬇ G ?

A
  • 1st IE
  • MP
  • Electronegativity
78
Q
  • its not abt the masses that react,
A

its abt no. of moles

79
Q

how to test for H2 gas?

A

squeaky pop test

80
Q

reactions of Limewater - cloudy, then clear?

A
  • cloudy - Ca Hydrox + CO2 -> CaCO3 + water
  • CaCO3 is insoluble, white precipitate
    clear = CaCO3 + H2O + CO2 -> Ca(HCO3)2 - soluble product
81
Q

G2 elements physical properties?

A
  • all G2 have similar physical properties
  • relatively high MP & BP
  • generally low density, light materials
  • form white compounds
82
Q

reaction of G2 with oxygen need to be ____ to start?

A

heated

- w/o heat slow reaction will occur

83
Q

All G2 elements react with water except ?

A
  • Beryllium

- others react to form hydroxides and H gas

84
Q

all G2 react with dilute acids except?

A

Beryllium

85
Q

why will a solution of these metal hydroxides be alkaline?

A
  • they r soluble in water

- they will release Hydroxide ions

86
Q

trend in reactivity of G2 sulphates?

A
  • ⬇ G, solubility of sulphates decreases
87
Q

Magnesium Hydroxide is also known as ?

A

milk of magnesia

88
Q

why are G2 compounds used?

A

hydroxides, oxides, carbonates are basic, can neutralise acids

89
Q

g2 metals can also be used in?

A

titanium extraction

90
Q

Ca uses?

A
  • building materials - limestone and marble used in construction - both contain cal carbonate
  • buildings made of these will gradually erode as CaCo3 will react with acids in rainwater
91
Q

Ba uses?

A
  • Barium Meal
  • Ba2+ poisounous to humans, but aren’t free to move
  • so Ba sulf can be safely ingested
  • helps with visualisation of soft tissue on X ray
  • often used in GI tract imaging - identifies blockages ect
92
Q

down G7 electronegativity ?

A
  • decreases
  • outer e held further away from nucleus
    ( F most elecronegative elemrnt)
93
Q

advantages of the chlorination of water?

A
  • sanitises water

- prevents spread of infection: espec: water bourne diseases like cholera

94
Q

disadvantages of the chlorination of water?

A
  • water is chlorinated before reaching the customer - potentially w/o their direct consent
  • possible that cl would react with organic matter forming chlorinated hyrocarbons - thought to cause cancer
  • chlorine is a toxic gas
95
Q

Halogens/ halides

agents

A
  • halogens = oxidising agents

- halide ions = reducing agents

96
Q

down G7

haogen/ halides - agents

A
  • ⬇ G, oxidising ability of halogens decreases

- ⬇ G, reducing power of halide ion increases

97
Q

halides with water?

A

form colourless acidi solutions:

Hydrofluoric, hydrochloric, hydrobromic, hydroiodic acid ect…

98
Q

carbonate test can also be done for?

A

hydrogen carbonate ions

99
Q

suphate test?

A

barium sulfate formed

  • insoluble
  • so white precipitate
100
Q

wat does adding nitric acid do?

A
  • removes any soluble impurities, wich could interefre w results
  • incl: carbonates - woulf form insoluble silver carbonate
  • & hydroxides - would form silver hydroxide
101
Q

why is the halide test not used on fluoride ions?

A
  • silver fluoride IS soluble
102
Q

order of tests? (G7)

A
  1. Carbonate
  2. Sulfate
  3. Halide
103
Q

reason for test order?

A
  • carbonate test must be done b4 sulfate as BaCO3 is insoluble and not easily distnguishabe from barium sulfate
  • the sulfate test must be done b4 halide test as silver sulfate is insoluble and could be mistaken for a silver halide
104
Q

halide test results?

A
  • silver chloride: white
  • silver bromide: cream
  • silver iodide: yellow
    (white ppl add chlorine to swimming pools)

A level Chemistry (39 decks)

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