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Chemistry > Group 2 And 7 > Flashcards

Group 2 And 7 Flashcards

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1
Q

Why are the group 2 metals placed in the s block?

A

-outermost/highest energy electron is in the s orbital

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2
Q

Why does melting point decrease down the group?

A

-ionic radius increases so ions become less charge dense
-weaker ESFA between cations and delocalised electrons

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3
Q

Why does reactivity increase down Group 2

A

-In chemical reactions group 2 metals lose 2 electrons
-extra energy level every time so shielding and atomic radius increase
-weaker ESFA between nucleus and outermost e- so more easily lost

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4
Q

What type of reaction is a group 2 metal with cold water?

A

-Redox

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5
Q

State the equation for a group 2 metal and cold water

A

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

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6
Q

What is magnesium hydroxide known as?

A

-milk of magnesia
-used in indigestion tablets to neutralise excess stomach acids

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7
Q

What is calcium hydroxide known as?

A

-slaked lime
-used to reduce the acidity of soil

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8
Q

Are group 2 reactions with steam more or less vigorous than those with cold water?

A

More

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9
Q

What type of reaction is a group 2 metal with steam?

A

-Redox

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10
Q

State the reaction of a group 2 metal with steam

A

M(s) + H2O (g) -> MO(s) + H2(g)

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11
Q

What colour are all the insoluble group 2 hydroxides?

A

White

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12
Q

The solubility of group 2 hydroxides…

A

Increase down the group

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13
Q

Mg(OH)2 is almost…

A

Insoluble and may be sold as a suspension in water

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14
Q

Ca(OH)2 is sparingly…

A

Soluble and may be sold in solution as limewater

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15
Q

What is the formula for limewater?

A

Ca(OH)2

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16
Q

What colour are the insoluble group 2 sulphates?

A

White

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17
Q

How does solubility of the group 2 sulphates change down the group?

A

Decrease

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18
Q

What is barium sulphate known as?

A

A barium meal

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19
Q

Why is it safe to ingest barium sulphate despite it being highly toxic?

A

Because it is so insoluble

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20
Q

What is barium meal used for?

A

To outline the gut in medical x rays

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21
Q

What else can barium sulphate be used for?

A

-to test the presence of sulphate ions in an unknown sample

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22
Q

Why is a solution acidified with nitric or hydrochloric acid before testing for sulphate ions?

A

-to get rid of any carbonate ions that may interfere with the experiment
-barium carbonate would be formed

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23
Q

What do you do after you acidify the solution to test for sulphate ions?

A

-add barium chloride
-if a white precipitate (BaSO4) forms that’s means sulphate ions are present

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24
Q

What is the ionic equation for barium and sulphate ions?

A

Ba2+ + SO42- -? BaSO4

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25
Q

What else can magnesium be used for?

A

-Production of titanium

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26
Q

How is titanium extracted?

A

-titanium ore is converted to titanium chloride which is then reduced to titanium by reaction w/ magnesium

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27
Q

State the equation for reduction of titanium chloride using magnesium

A

TiCl4 + 2Mg -> Ti + 2MgCL2

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28
Q

What can calcium oxide to be used for?

A

Flue gas desulfurisation

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29
Q

What type of reaction is CaO with SO2?

A

Acid-base

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30
Q

Before flue-gases are released into the atmosphere they are…

A

Scrubbed with calcium oxide

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31
Q

State the reaction of calcium oxide with sulfur dioxide?

A

CaO + SO2 -> CaSO3

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32
Q

What type of structure do halogens have?

A

Simple molecular structure

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33
Q

What is electronegativity?

A

The ability of an atom to withdraw e- density towards itself in a covalent bond

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34
Q

How does electronegativity change down the group?

A

-decreases
-extra energy level each time so shielding and atomic radius increase
-weaker ESFA between nuclear and bonding electrons

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35
Q

The combination of reagents required to test for halide ions is:

A

(I) dilute nitric acid
(II)silver nitrate (AgNO3)

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36
Q

What is the purpose of dilute nitric acid in the tests for halide ions?

A

-to get rid of impurities such as carbonate
-carbonate would cause fizzing

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37
Q

When are the precipitates formed in a test for halide ions using silver nitrate?

A

-When aqueous Ag+ reacts with an aqueous halide ion X- to form a solid silver halid, AgX

Ag+ + X- -> AgX(s)

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38
Q

What silver halide does not form a precipitate as it is soluble?

A

Silver Fluoride
AgF

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39
Q

What is the white silver halide precipitate?

A

AgCl

40
Q

What is the cream silver halide precipitate?

A

AgBr

41
Q

What is the yellow silver halide precipitate?

A

AgI

42
Q

What is the only silver halide precipitate that dissolves in dilute ammonia

A

AgCl

43
Q

What is the equation of the reaction with silver chloride and ammonia?

A

AgCl + 2NH3 -> [Ag(NH3)2]+ + Cl-

44
Q

What is [Ag(NH3)2]+

A

-a silver complex present in toluene’s reagent
-silver ion with two ammonia molecules in a linear arrangement
-lone pairs on N atoms in the ammonia molecules form dative covalent bonds with silver ion in the centre

45
Q

How do you differentiate between AgBr and AgI

A

-add concentrated ammonia
-AgBr dissolves and AgI doesn’t

46
Q

What is the equation for the dissolving of AgBr?

A

AgBr (s) + 2NH3 -> [Ag(NH3)2] + Br-

47
Q

What is the trend in solubility of the silver halide down the group?

A

-decreases down the group

48
Q

What is oxidising power?

A

-ability to gain electrons

49
Q

Do halides or halogens have oxidising power

A

Halogens

50
Q

What is halogen displacement?

A

-when a more reactive halogen displaces a less reactive halogen from a solution of one of its salts

51
Q

What happens when Cl2 reacts with KBr

A

-colourless to orange
(Cl2 is a pale green solution)

52
Q

What colour change happens when Cl2 is added to Ki

A

Colourless to brown

53
Q

What colour change happens when Br2 is added to potassium iodide?

A

-colourless to brown
(Br2 is an orange solution)

54
Q

State the overall and ionic equation for Chlorine and potassium bromine

A

-Cl2 + 2Kbr -> 2KCl + Br2

-Cl2- + 2Br -> 2Cl- + Br2

55
Q

What is the strongest oxidising agent?

A

Cl2 as it can displace Br2 and I2

56
Q

How does oxidising power change down the group

A

Decreases

57
Q

why does oxidising power change down the group?

A

X2 + 2e- -> 2x-

-extra energy level each time
- increase in atomic radius and shielding
-weaker ESFA between nucleus and incoming electron so its harder to gain a electron

58
Q

How are relative oxidising or reducing powers of species quantified?

A

Using standard electrode potentials

59
Q

The more positive the value on the SEP the more feasible the…

A

Reduction process is

60
Q

What is the strongest oxidising agent?

A

F2

61
Q

What is the weakest oxidising agent?

A

I2

62
Q

What is the strongest reducing agent?

A

I-

63
Q

What is the weakest reducing agent?

A

F-

64
Q

What is reducing power?

A

-the ability to reduce
-ability to be oxidised

65
Q

When we are looking at reducing power we look at the ease with which the following process occurs:

A

2X- -> X2 + 2e-

66
Q

How does reducing power change down the group?

A

Increases

67
Q

What happens where KCL is added to H2SO4

A

Observations:
-white fumes
-effervesence
HCl

68
Q

What is the equation for KCl and H2SO4

A

H2SO4 + KCl -> KHSO4 + HCl

69
Q

Is the reaction between sulphuric acid and potassium chloride redox?

A

No
-no change in oxidation state
‘Cl- will not reduce H2SO4’

This is an acid-base reaction

70
Q

What happens when you add KBr to H2SO4

A

-White fumes (HBr)
-Effervesence (SO2) (choking gas)
-orange vapour (Br2)

71
Q

How many equations are there for the reaction between KBr and H2SO4

A

2
-redox
-acid base

72
Q

What is the acid base reaction between H2SO4 and KBr

A

H2SO4 + KBr -> KHSO4 + HBr

73
Q

What does a reaction between H2SO4 and KBr produce?

A

HBr
Br2 (redox)
SO2 (redox)

74
Q

Why is Br- and better reducing agent than Cl-?

A

As there is a redox reaction with conc H2SO4

75
Q

What observations are there when KI is added to H2SO4

A

-effervesence (choking gas) (SO2)
-white fumes (HI)
-yellow solid (S)
-black solid (I2)
-rotten egg smell (H2S)

76
Q

Whart is the Acid-base reaction when potassium iodide is added to sulphuric acid?

A

KI + H2SO4 -> KHSO4 + HI

77
Q

Why do we know iodide is the most powerful reducing agent?

A

-I- can reduce S in H2SO4 from +6 down to +4 (in SO2,) 0 (in S) and -2 (in H2S)

78
Q

Why does reducing power of the halides change down the group?

A

-ionic radius increases (extra energy level each time)
-shielding increases
-weaker ESFA between nucleus and outer e-
-e- lost more easily

79
Q

What happens when Cl2 is bubbled into water?

A

-A pale green solution is formed

80
Q

What is the equation for when chlorine is bubbled into water?

A

Cl2 + H2O <—> HCl + HClO

81
Q

What is HClO?

A

Chloric (I) acid

82
Q

What type of reaction is the reaction of Cl2 with H2O?

A

Disproportional reaction

83
Q

What happens in a disproportionate reaction?

A

When one species is simultaneously oxidised and reduced

84
Q

ClO- is a powerful…

A

Bleach

85
Q

Where does the reaction of Cl2 with H2O take place?

A

-swimming pools and drinking water
-ClO- is an oxidising agent that kills bacteria

86
Q

Why is chlorine still ok to treat water despite it being toxic?

A

-only used in small amounts
-health benefits outweigh the risk

87
Q

Rewrite Cl2 + H2O <—> HCl + HClO

A

Cl2 + H2O <—> 2H+ + Cl- + ClO-

88
Q

What happens to the yield of ClO- ions if acid (H+) is added?

Cl2 + H2O <–> 2H+ + Cl- + ClO-

A

-Le Chateliers principle
-Reaction works to remove added H+
-Backwards reaction favoured
-POE moves to left
-Yield of ClO- decreases

89
Q

Using Le Chateliers principle, how would the system rep one if NaOH was added?

Cl2 + H2O <–> 2H+ + Cl- + ClO-

A

-When OH- is added, OH- reacts w/ H+ ions, removing them
-Reaction works to replace lost H+
-forwards reaction favoured
-POE moves to RHS
-yield of ClO- increases

90
Q

Why is NaOH added to swimming pools?

A

-OH reacts with H+
-Forwards reaction favoured
-More ClO-
-More bacteria killed

91
Q

What is the reaction that takes place when NaOH is added to chlorine?

A

Cl2 + 2NaOH -> NaCl + NaClO + H2O

92
Q

What is the reaction of Cl2 with H2O in the presence of sunlight?

A

2Cl2 + 2H2O -> 4HCl + O2

93
Q

Why do outdoor swimming pools require more frequent additions of chlorine

A

-Chlorine is lost from swimming pools

94
Q

What is an alternative to the direct chlorination of swimming pools?

A

-Add sodium chlorate
-Dissolves in water to form chloric acid

NaClO + H2O -> NaOH + HCLO

95
Q

Why do pools that are treated with Sodium Chlorate require a pH less than 7?

A

-H+ reacts with OH- (in NaOH) removing OH- reaction works to replace lost OH-
-forward reaction favoured
-P.o.E moves to RHS
-increased yield of HCLO (CLO- kills bacteria)

96
Q

What is NaCLO?

A

Sodium Chlorate

Chemistry (13 decks)

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