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Chemistry - Dr Sayed > halogens > Flashcards

halogens Flashcards

1
Q

F2 colours + reactivity

A

very pale yellow gas

highly reactive

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2
Q

Cl2 colours + reactivity

A

greenish
reactive gas
poisonous in high con

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3
Q

Br2 colours + reactivity

A

red liquid

dense brown/orange poisonous fumes

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4
Q

I2 colours + reactivity

A

shiny grey solid

sublimes to purple gas

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5
Q

trend in boiling + melting point

A

increases down group
molecules get larger = more electrons
=larger van der waals between molecules
larger intermolecular force = more energy needed to break forces

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6
Q

define electronegativity

A

relative tendency of a molecule to attract a bonding pair of electrons to itself in a covalent bond.

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7
Q

trend in electronegativity

A

decreases down group
atomic radii increases down group as no. of shells increase
= nucleus less able to attract bonding pair of electrons

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8
Q

what are oxidising agents

A

electron acceptors

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9
Q

does oxidising strength increase or decrease down group?

A

decrease

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10
Q

what will a halogen that is a stronger oxidising agent do?

A

replace a halogen with less oxidising power

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11
Q

what colour does chlorine have if it’s a free halogen in a displacement reaction

A

very pale green

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12
Q

what colour does bromine have if it’s a free halogen in a displacement reaction

A

yellow solution

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13
Q

what colour does iodine have if it’s a free halogen in a displacement reaction

A

brown solution

sometimes black solid

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14
Q

write the half equations for the displacement reaction for Cl2(aq) + 2Br –(aq) → 2Cl –(aq) + Br2(aq)

A

2Br - (aq)→ Br2(aq)+ 2e-

Cl2(aq)+ 2e- → 2Cl- (aq)

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15
Q

why is a halide ion with silver nitrate test used

A

to identify the halide ion

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16
Q

what chemicals are used in a silver nitrate test

A

nitric acid - to make solution acidic

silver nitrate - added dropwise

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17
Q

what is the role of nitric acid in a silver nitrate test

A

react with carbonates present

to prevent ppt of Ag2Co3- would mask desired products

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18
Q

write the reaction between nitric acid and sodium carbonate

A

2 HNO3 + Na2CO3 →2 NaNO3 + H2O + CO2

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19
Q

what do fluorides produce with silver nitrate and nitric acid

A

no ppt

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20
Q

what do chlorides produce with silver nitrate and nitric acid

A

white ppt

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21
Q

write the ionic equation for the reaction of chlorine with silver nitrate and citric acid

A

Ag+(aq) + Cl- (aq) → AgCl(s)

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22
Q

what do bromides produce with silver nitrate and nitric acid

A

cream ppt

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23
Q

write the ionic equation for the reaction of bromine with silver nitrate and citric acid

A

Ag+(aq) + Br- (aq) → AgBr(s)

24
Q

what do iodides produce with silver nitrate and nitric acid

A

pale yellow ppt

25
Q

write the ionic equation for the reaction of iodine with silver nitrate and citric acid

A

Ag+(aq) + I- (aq) → AgI(s)

26
Q

what does silver chloride dissolve in

A

dilute ammonia

27
Q

what does silver bromide dissolve in

A

concentrated ammonia

28
Q

what does silver iodide dissolve in

A

doesn’t react with ammonia - too insoluble

29
Q

trend in reducing power down the group and why

A

increasing power
ions bigger, outer electrons further from positive nucleus
extra inner electrons provide shielding

30
Q

what type of reaction takes place between H2SO4 and Cl and why

A

acid- base

cl is not strong enough of a reducing agent

31
Q

write the equation for the reaction between H2SO4 and Cl

A

NaCl(s) + H2SO4(l) → NaHSO4(s) + HCl(g)

32
Q

what observations in H2SO4 + Cl reaction

A

white steamy fumes

of HCL

33
Q

what type of reaction takes place between H2SO4 and F and why

A

acid- base

F is not strong enough of a reducing agent

34
Q

write the equation for the reaction between H2SO4 and F

A

NaF(s) + H2SO4(l) →NaHSO4(s) + HF(g)

35
Q

what observations in H2SO4 + F reaction

A

white steamy fumes

of HF

36
Q

what is the role of H2SO4 in acid-base reactions

A

the acid

37
Q

what is an acid

A

proton donor

38
Q

what is a base

A

proton acceptor

39
Q

write the acid-base step between Br and H2SO4

A

NaBr(s) + H2SO4(l) → NaHSO4(s) + HBr(g)

40
Q

write the redox step between Br and H2SO4

A

2 HBr + H2SO4 → Br2(g) + SO2(g) + 2 H2O(l)

41
Q

write the redox equations for Br and H2SO4

A

Ox ½ equation 2Br - → Br 2 + 2e-

Re ½ equation H2SO4 + 2 H+ + 2 e- → SO2 + 2 H2O

42
Q

what is the role of H2SO4 in the redox step

A

oxidising agent

43
Q

what observations for Br and H2SO4

A

HBr ; white steamy fumes
Br2 ; orange fumes
S02 ; odourless, acidic

44
Q

write the acid-base step between I and H2SO4

A

NaI(s) + H2SO4(l) → NaHSO4(s) + HI(g)

45
Q

write the redox stepS between I and H2SO4

A

2 HI + H2SO4 → I2(s) + SO2(g) + 2 H2O(l)
6 HI + H2SO4 → 3 I2 + S (s) + 4 H2O (l)
8 HI + H2SO4 → 4 I2(s) + H2S(g) + 4H20 (l)

46
Q

write the redox equations for I and H2SO4

A

Ox ½ equation 2I - → I2 + 2e-
Re ½ equation H2SO4 + 2 H+ + 2 e- → SO2 + 2 H2O
Re ½ equation H2SO4 + 6 H+ + 6 e- → S + 4 H2O
Re ½ equation H2SO4 + 8 H+ + 8 e- → H2S + 4 H2O

47
Q

what observations for I and H2SO4

A 
HI ; white steamy fumes
I2 ; black solid/purple fumes
S02 ; colourless, acidic gas
S ; yellow solid
H2S ; gas with bad egg smell
48
Q

write the reaction between Cl and water

A

Cl2(g) + H2O (l) ⇌ HClO (aq) + HCl (aq)

49
Q

write the reaction between Cl and water in sunlight

A

2Cl2 + 2H2O → 4H+ + 4Cl- + O

50
Q

what is chlorine in water used for

A

to kill bacteria, prevent reinfection + growth of algae

51
Q

write the reaction between Cl2 and cold dilute NaOH

A

Cl2(aq) + 2 NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (l)

52
Q

what is NaClO

A

sodium chlorate (I)

53
Q

what is NaClO3

A

sodium chlorate (V)

54
Q

what is K2So4

A

potassium sulfate(VI)

55
Q

what is K2SO3

A

potassium sulfate(IV)

Chemistry - Dr Sayed (7 decks)

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