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chemistry: inorganic chemistry 1 > group 7 > Flashcards

group 7 Flashcards

1
Q

what are the physical property of flourine?

A

pale yellow gas

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2
Q

what is the physical property of chlorine?

A

green / yellow gas

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3
Q

what is the physical property of bromine?

A

orange / brown liquid

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4
Q

what is the physical property of iodine?

A

grey / black solid

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5
Q

what happens to atomic radius down group 7?

A

increases

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6
Q

why does atomic radius increase down group 7?

A

extra filled electron shell

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7
Q

what happens to electronegativity down group 7?

A

decreases

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8
Q

why does electronegativity decrease down group?

A

● larger atomic radius

● more shielding

● weaker attraction of outer e- to positive nucleus

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9
Q

what happens to melting and boiling point down group 7?

A

increases

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10
Q

why does melting and boiling point increase down group 7?

A

● atoms get larger

● more electrons

● stronger van der waals forces

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11
Q

how to identify halide ions?

A

with silver (Ag+) ions

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12
Q

what metal halides don’t react with Ag+ ions in solution?

A

fluorides

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13
Q

what precipitate do chlorine ions form?

A

white ppt (forms slowest)

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14
Q

what precipitate do bromine ions form?

A

pale cream ppt

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15
Q

what precipitate do iodine ions form?

A

pale yellow ppt (forms fastest)

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16
Q

what is the general ionic equation for the formation of the insoluble precipitate?

A

X- (aq) + Ag+ (aq) -> AgX(s)

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17
Q

what is the method for identifying the halide ions?

A

● add dilute nitric acid to halide solution

● add a few drops of silver nitrate solution

● observe precipitates that form

● add dilute and conc ammonia to distinguish between precipitates

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18
Q

why do we add dilute nitric acid to halide solution?

A

● to remove any soluble carbonate or hydroxide impurities

● carbonate ions form silver carbonate

● hydroxide ions form insoluble silver hydroxide

● interfering with the test

● if carbonate ions are present effervescence is observed

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19
Q

which precipitate dissolves / is soluble in dilute ammonia?

A

AgCl (most soluble)

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20
Q

which precipitate dissolves / is soluble in conc ammonia?

A

AgBr

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21
Q

which precipitate does not dissolves / is insoluble in both dilute and conc ammonia?

A

AgI (least soluble)

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22
Q

what do we mean by reducing power?

A

● how good a halide ion is at being a reducing agent

● halide ions react by losing electrons

● so, being oxidised

23
Q

what is the trend in reducing power down group 7?

A

increases

24
Q

why does reducing power increase down group 7?

A

● easier to lose an electron as

● ions are larger

● more shielding

● therefore, weaker attraction of outer e- to positive nucleus

● which explains their reaction with sulfuric acid

25
Q

explain the reaction of NaCl with H2SO4

A

● equation: NaCl + H2SO4 -> NaHSO4 + HCl

● product: HCl

● observation: steamy fumes

● reaction type: acid base

26
Q

why is the reaction between NaCl and H2SO4 not a redox?

A

● no change in oxidation states of chloride and sulfur (-1 and +6)

● chloride is not a strong enough reducing agent to reduce sulfuric acid

27
Q

explain the reactions of NaBr and HBr with H2SO4

A

● equations:
NaBr + H2SO4 -> NaHSO4 + HBr
2Br-(-1) + H2SO4 (+6)+ 2H+ -> Br2 (0) + SO2(+4) + 2H2O

● products: HBr, Br2, SO2

● observation:
HBr - steamy fumes
Br2 - brown fumes
SO2 - colourless gas

● reaction type:
HBr - acid-base
Br2 - oxidation of Br-
SO2 - reduction of H2SO4

28
Q

why is the reaction between HBr and H2SO4 a redox reaction?

A

● bromide is a strong enough reducing agent to reduce H2SO4 to SO2

● sulfur is reduced from +6 in H2SO4 to +4 in SO2

● bromine is oxidised from -1 in Br- to 0 in Br2

29
Q

explain the reaction of NaI and HI with H2SO4

A

● equations:
NaI + H2SO4 -> NaHSO4 + HI
2I- (-1) + H2SO4(+6) + 2H+ -> I2 (0) + SO2 (+4) + 2H2O
6I- + H2SO4 (+6) + 6H+ -> 3I2 + S (0) + 4H2O
8I- + H2SO4 (+6) + 8H+ -> 4I2 + H2S (-2) + 4H2O

● products: HI, I2, SO2, S, H2S

● observation:
HI - steamy fumes
I2 - purple fumes
SO2 - colourless gas
S - yellow solid
H2S - gas (bad egg smell)

● reaction type:
HI - acid-base
I2 - oxidation of I-
SO2 - reduction of H2SO4
S - reduction of H2SO4
H2S - reduction of H2SO4

30
Q

why is the reaction between HI and H2SO4 a redox reaction?

A

● HI is a very strong reducing agent

● iodine is is oxidised from -1 in I- to 0 in I2

● sulfur is reduced from +6 in H2SO4 to +4 in SO2

● sulfur is reduced from +6 in H2SO4 to 0 in S

● sulfur is reduced from +6 in H2SO4 to -2 in H2S

31
Q

what do we mean by oxidising power?

A

● how good halogen is at being an oxidising agent

● halogens react by gaining electrons

● so, being reduced

32
Q

why does oxidising power decrease down the group?

A

● becomes harder to gain an electron

● as atoms have a larger atomic radius

● more shielding due to an extra electron shell

33
Q

what is the trend in oxidising power of the halogens down the group?

A

decreases

34
Q

what is the basic rule for halogen displacement reactions?

A

a halogen will displace a halide from a solution if the halide is below it in the periodic table

35
Q

what happens in a displacement reaction between chlorine and bromide?

A

● orange solution formed

● bromide displaced

36
Q

what happens in a displacement reaction between chlorine and iodide?

A

● brown solution formed

● iodide displaced

37
Q

what happens in a displacement reaction between bromine and iodide?

A

● brown solution formed

● iodide displaced

38
Q

does iodine react with F-, Cl- or Br-?

A

no

39
Q

where can bromine be extracted from?

A

sea water

40
Q

how can bromine be extracted from sea water?

A

● sea water has bromine ions

● which can be oxidised by chlorine to give bromine

41
Q

what is the equation for the extraction of bromine from sea water?

A

Cl2 (aq) + 2Br- (aq) -> 2Cl- (aq) + Br2(aq)

42
Q

where can iodine be extracted from?

A

kelp

43
Q

how can iodine be extracted from kelp?

A

● salts (NaCl, KCl, K2SO4) removed from kelp

● by washing with water

● residue heated with manganese dioxide

● and conc sulfuric acid

44
Q

what is the equation for the extraction of iodine from kelp?

A

2I- + MnO2 + 4H+ -> Mn2+ + I2 + 2H2O

45
Q

what is disproportionation?

A

when oxidation states of some atoms of the same element increase and others decrease

46
Q

what is the equation for when chlorine reacts with water?

A

Cl2 (g) (0) + H2O (l) ⇌ HClO (aq)(+1) + HCl (aq) (-1)

47
Q

what happens when chlorine reacts with water?

A

● reversible reaction occurs

● oxidation state of chlorine increase from 0 in Cl2 to +1 in HClO

● oxidation state of chlorine decreases from 0 to -1 in HCl

● example of disproportionation

48
Q

what is the reaction between chlorine and water used for?

A

● water purification

● for drinking and swimming pools

● chloric acid is an oxidising agent

● which kills bacteria by oxidation

49
Q

what is the equation for the reaction of chlorine and water in sunlight?

A

2Cl(g) (pale green) + 2H2O(l) -> 4HCl (aq) (colourless) + O2 (g)

50
Q

why does chlorine have to be added to pools in sunlight frequently?

A

chlorine is lost rapidly from pools in sunlight

51
Q

what is an alternative to chlorination?

A

● adding solid sodium or calcium chlorate

● NaClO (s) + H2O (l) ⇌ Na+ (aq) + OH- (aq) + HClO(aq)

● sodium chlorate dissolves in water to give chloric acid

● in alkali conditions, equilibrium shifts to left and removes HClO (as ClO- ions)

● pools must be kept slightly acidic using this method - carefully monitored

52
Q

what happens when chlorine reacts with an alkali?

A

● alkali: sodium hydroxide

● which must be cold and dilute

● products: sodium chlorate, sodium chloride and water

● sodium chlorate is an OA

● and active ingredient in bleach

53
Q

what is the equation for the reaction of chlorine and sodium hydroxide?

A

Cl2(g) (0) + 2NaOH (aq) -> NaClO(aq) (+1) + NaCl (aq) (-1) + H2O (l)

54
Q

what is this reaction an example of?

A

● disproportionation reaction as

● in NaClO, Cl has an oxidation state of +1 and in NaCl, Cl has an oxidation state of -1

chemistry: inorganic chemistry 1 (5 decks)

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