Group 7 Flashcards

1
Q

Explain the trend in boiling point of group 7:

A
  • There are Van der Waals forces between molecules
  • The molecules get larger as you go down the group as there’s more electrons
  • Therefore there’s stronger Van Der Waals forces between molecules
  • So there’s more energy required to overcome the intermolecular forces
  • Therefore the boiling point increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain the trend in atomic/ionic radius in group 7:

A
  • Number of filled shells increases so the shielding increases
  • Forces of attraction between the nucleus and outer electrons decreases
  • Therefore atomic radius increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain the trend in electronegativity in group 7:

A
  • Shielding increases
  • Nuclear charge increases
  • Atomic radius increases
  • Forces of attraction between nucleus and outer electrons decreases
  • Therefore, electronegativity decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain the trend in reactivity in group 7:

A
  • Shielding, atomic radius increases
  • Forces of attraction between the nucleus and outer electrons decreases
  • It’s harder to gain an electron
  • Reactivity decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does oxidising power mean?

A

How good it is at accepting electrons.
(An oxidising agent is the one that’s reduced).

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

Predict and explain the trend in oxidising power of the halogens:

A

(Strongest) F2 > Cl2 > Br2 > I2 (Weakest)

It’s essentially the same as reactivity.

  • Shielding increases
  • Atomic radius increases
  • Forces of attraction between nucleus and outer electrons decreases
  • Harder to accept electrons so their oxidising power decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the appearance of chlorine gas and chlorine water

A

Pale yellow green gas
Very pale green solution, often colourless

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the appearance of bromine water

A

Orange-brown liquid
A gas can form brown fumes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the appearance of Iodine:

A

Brown solution/ Black solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the appearance of flourine:

A

Pale yellow gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe and explain the trend of reducing powers of halide ions:

A
  • Increases
  • More shells, more shielding, atomic radius increases
  • Weaker forces of attraction between nucleus and outer electrons
  • So it’s easier to lose those electrons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does F- not act as a reducing agent?

A
  • Fewer shells/ little shielding
  • Small ionic radius
  • Very strong forces of attraction between nucleus and outer electrons
  • Requires a lot of energy to lose those electrons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Concentrated H2SO4 can be further reduced by which halide ions?

A

Bromide ions
Iodide ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why can’t chlorine reduce sulfuric acid?

A

It’s not a strong enough reducing agent

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

What can bromide ions reduce sulfuric acid into?

A

SO2

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

What can iodide ions reduce sulfuric acid into?

17
Q

What are the observations when bromide ions reduce sulfuric acid into SO2?

A
  • Brown fumes of Br2
  • SO2 is colourless (There’s no observation)
18
Q

What are the observations when iodide ions reduce sulfuric acid into S?

A
  • Black solid Iodine
  • S is a yellow solid
19
Q

What are the observations when iodide ions reduce sulfuric acid into sulfur?

A

S = yellow solid
I2 = black solid

20
Q

What are the observations when iodide ions reduce sulfuric acid into H2S?

A

Bad egg smell (H2S)
Black solid = I2

21
Q

When answering exam questions on testing for halides, what should you be careful of?

A

In exam questions, they often start with solids. So make sure the first step in a method is to add water to make a solution.

22
Q

How do we test for halides?

A
  • Place a solution of the halide in a test tube, 5cm3
  • Add 1cm3 dilute nitric acid. This removes any other ions that could give a precipitate with silver nitrate.
  • Add silver nitrate solution
  • White, cream or yellow precipitate formed
  • treat any precipitate with dilute ammonia solution
  • if precipitate still exists, add concentrated ammonia
23
Q

Which halide makes a white precipitate?

24
Q

Which halide gives a cream precipitate?

25
Which halide gives a yellow precipitate?
Iodide
26
Why do we use nitric acid and not something like HCL?
HCL would react with the silver and precipitate.
27
What do you observe when you add: - dilute NH3 - Concentrated NH3 to Agcl?
AgCl dissolves in both
28
What do you observe when you add: - dilute NH3 - Concentrated NH3 to AgBr?
Dilute NH3; - does not dissolve Conc: - dissolves
29
What do you observe when you add: - dilute NH3 - Concentrated NH3 to AgI?
Dilute NH3: Does not dissolve Conc. Does not dissolve (Think of it as the halogens become less reactive as you go down the group).
30
Why have we not mentioned flouride ions in the test for halides?
AgF is soluble in water. You cannot test for F- using silver nitrate.
31
dfd