The halogens Flashcards

1
Q

in which block are the halogens

A

p-block

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

state and colour of fluorine

A

pale yellow gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

state and colour of chlorine

A

green gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

state and colour of bromine

A

red-brown liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

state and colour of iodine

A

black solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what factors increase down group 7

A
  • nuclear charge
  • number of e-
  • atomic radius
  • boiling point
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why does the boiling point of the halogens increase down the group

A
  • more electrons moving down the group, strength of the temporary dipoles increases.
  • Increased dipoles mean greater London forces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what type of reactions are halogens often involved in

A
  • redox reactions
  • they gain 1 e- to form 1- halide ion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why does electronegativity decrease down group 7

A
  • increase in atomic radii
  • shielding outweighs the increase in nuclear charge
  • less attraction between nucleus and valent e-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

why is fluorine the most reactive

A
  • atomic radius increases down the group
  • greater shielding
  • less nuclear attraction to attract an electron from another species
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what happens when a more reactive and less reactive halogen react

A
  • more reactive halogen will displace a less reactive halide ion from solution resulting in a colour change corresponding to the displaced halogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why are halogens less reactive down group 7

A
  • decreasing electronegativity reduces halogen’s ability to attract and e- to form 1- ion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what can be done to make colour change in displacement reactions easier to see

A
  • in a separating funnel, shake the reaction mixture with an organic solvent like hexane
  • non-polar halogen dissolves in non-polar organic solvent
  • polar halide dissolves in aq layer
  • organic layer above aq
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what colour is chlorine in water

A

pale green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what colour is bromine in water

A

orange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what colour is iodine in water

A

brown

17
Q

in non-polar organic solvent chlorine is

A

pale yellow-green

18
Q

in non-polar organic solvent iodine is

A

purple

19
Q

in non-polar organic solvent bromine is

A

yellow-orange

20
Q

ionic equations for displacement reactions

A

X2 (aq) + 2Y- (aq) –> Y2(aq) + 2X- (aq)
- the more reactive species ends up as ions

21
Q

are halogens oxidising or reducing agents

A

they’re oxidising agents and become reduced themselves

22
Q

define disproportionation

A

when a single element is simultaneously oxidised and reduced in a reaction

23
Q

equation for the disproportionation of chlorine when reacted with water

A

Cl2(aq) + H2O(l) —> HCl (aq) + HClO(aq)
- Cl reduced from 0 in Cl2 to -1 in HCl
- Cl oxidised from 0 in Cl2 to +1 in HClO

24
Q

why is chlorine used in water purification

A

on addition to water, the products, chloric (I) acid, HClO, and the Cl- ion, effectively kill bac

25
Q

advantages of chlorinating water

A
  • sanitises water by killing bac
  • prevents the spread of waterborne diseases
26
Q

disadvantages of chlorinating water

A
  • may react with hydrocarbons to form carcinogenic chlorinated hydrocarbons
  • Cl2 is a toxic gas and can irritate the respiratory system in low conc
27
Q

what kind of reaction occurs when chlorine reacts with cold, dilute NaOH and give the equation

A
  • disproportionation
  • Cl2(g) + 2NaOH(aq) —> NaCl(aq) + NaClO(aq) + H2O(l)
  • 0 in Cl2 to -1 in NaCl and +1 in NaClO
  • NaClO is the active ingredient in bleach
28
Q

test for halides

A
  • add AgNO3
  • Cl- produces white ppt (AgCl)
  • Br- produces cream ppt (AgBr)
  • I- produces yellow ppt (AgI)
29
Q

silver halides can be hard to distinguish so what’s is added to distinguish them clearly

A

NH3

30
Q

how can you tell if ppt is AgCl

A

soluble in dilute NH3

31
Q

how can you tell if ppt is AgBr

A

soluble in conc NH3

32
Q

how can you tell if ppt is AgI

A

insoluble in conc NH3