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chemistry > topic 4B > Flashcards

topic 4B Flashcards

1
Q

reactivity of group 7 halogens

A

reactivity increases down the group

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2
Q

trend in melting and boiling point

A
  • increases down the group
  • as molecules become larger they have more electrons so larger London forces between molecules
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3
Q

trend in electronegativity

A
  • electronegativity of the elements decreases
  • atomic radii increases down the group due to increasing shells
  • hence nucleus less able to attract the bonding pair of electrons
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4
Q

trend in reactivity

A

reactivity decreases down the group
- as atoms get bigger, they less easily attract and accept electrons

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5
Q

oxidation reactions of halide ions by halogens

A
  • a halogen that is a strong oxidising agent will displace a halogen that has a lower oxidising power
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6
Q

oxidation strength down the group

A

decreases

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7
Q

colour of chlorine in solution

A

very pale green (often colourless)

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8
Q

colour of bromine in solution

A

yellow solution

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9
Q

colour of iodine in solution

A

brown solution (sometimes black solid)

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10
Q

colour of organic solvent layer - chlorine

A

colourless

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11
Q

colour of organic solvent layer - bromine

A

yellow

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12
Q

colour of organic solvent layer - iodine

A

purple

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13
Q

reaction of chlorine with water

A

Cl2 + H2O –> HClO + HCl

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14
Q

what happens if universal indicator is added to solution

A

First turns red due to acidity of both reaction products.
Then goes colourless as the HClO bleaches the colour.

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15
Q

what is chlorine used for in water

A

Used to kill bacteria
Used in swimming pools

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16
Q

reactions of halogens with cold dilute NaOH solution

A

Cl2, Br2, I2
colour goes colourless
Cl2 + 2NaOH -> NaCl + NaClO + H2O
products used as bleach

17
Q

reaction of halogens with hot dilute NaOH

A

3Cl2 + 6NaOH -> 5NaCl + NaCLO3 + 3H2O

(same products for other halogens)

18
Q

Fluoride reaction with H2SO4 & observation

A

NaF + H2SO4 -> NaHSO4 + HF
observation: white steamy fumes of HF

19
Q

Chlorine reaction with H2SO4 & observation

A

NaCl + H2SO4 -> NaHSO4 + HCl
observation: white steamy fumes of HCl

20
Q

Bromine reaction with H2SO4

A

acid-base step: NaBr+ H2SO4 -> NaHSO4 + HBr

redox step: 2HBr + H2SO4 -> Br2 + SO2 + 2H2O

21
Q

Bromine reaction with H2SO4 oxidation and redox half equation

A

ox: 2Br- –> Br2 + 2e-
red: H2SO4 + 2H+ + 2e- –> SO2 + 2H2O

22
Q

Bromine reaction with H2SO4 observation

A

white steamy fumes of HBr are evolved
red fumes of Bromine also evolve and colourless acidic gas SO2

23
Q

Iodine reaction with H2SO4

A

strongest reducing agent
NaI+ H2SO4 -> NaHSO4 + HI
2HI + H2SO4 -> I2 + SO2 + 2H2O
6HI + H2SO4 -> 3 I2 + S + 4 H2O
8HI + H2SO4 -> 4 I2 + H2S + 4 H2O

24
Q

Iodine reaction with H2SO4 - observation

A

white steamy fumes
black solide and purple fumes of Iodine
colourless acidic gas SO2
yellow solid - sulphur
H2S, gas with bad egg smell

25
Q

Iodine reaction with H2SO4 - reduction products

A

sulfur dioxide
sulfur
hydrogen sulfide

26
Q

reaction of fluoride ions with silver nitrate

A

no precipitate

27
Q

reaction of chloride ions with silver

A

white precipitate
Ag+ + Cl- -> AgCl

28
Q

reaction of bromide ions with silver nitrate

A

cream precipitate
Ag+ + Br- -> AgBr

29
Q

reaction of iodide ions with silver nitrate

A

pale yellow precipitate
Ag+ + I- -> AgI

30
Q

effect of light on silver halides

A

precipitates darken forming silvereff

31
Q

effect of ammonia on silver halides

34
Q

producing hydrogen halide

A

made by the reaction of solid sodium halide salts with phosphoric acid
white steamy fumese

35
Q

test for presence of carbonate, CO3 2- and

A

bubble gas through lime-water to test for CO2
add any dilute acid and observe effervescence

36
Q

testing for presence of sulfate

A

acidified BaCl2 used as reagent
white precipitate forms

37
Q

test for ammonium

A

react with NaOH forming NH3
ammonia gas can be identified by its smell or turning damp red litmus paper blue

chemistry (28 decks)

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