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Inorganic Chemistry > 2.3 Group 7 > Flashcards

2.3 Group 7 Flashcards

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1
Q

Describe Fluorine

A

very pale yellow gas. It is highly reactive

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2
Q

Describe chlorine

A

greenish, reactive gas, poisonous in high concentrations

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3
Q

Describe Bromine

A

red liquid, that gives off dense brown/orange poisonous fumes

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4
Q

Describe Iodine

A

shiny grey solid sublimes to purple gas.

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5
Q

What happens to melting and boiling points as you go down group 7?

A

Increases

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6
Q

What is the trend of electronegativity as you go down group 7?

A

Decreases

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7
Q

What happens to oxidising strength as you go down group 7?

A

Decreases

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8
Q

What colour is chlorine in solution?

A

Very pale green (often colourless)

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9
Q

What colour is bromine in solution ?

A

Yellow solution

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10
Q

What colour is Iodine in solution?

A

Brown (something black solid present)

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11
Q

How do you identify halide ions?

A

Solution made acidic with nitric acid and then silver nitrate solution is added dropwise

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12
Q

Why is nitric acid added to the halide solution?

A

The role of nitric acid is to react with any carbonates present to prevent formation of the precipitate Ag2CO3. This would mask the desired observations

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13
Q

Halide ion test for fluorine

A

No precipitate

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14
Q

Halide ion test for chlorides

A

White precipitate

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15
Q

Halide ion test for bromides

A

Cream precipitate

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16
Q

This question is about elements in Group 7 of the Periodic Table and their compounds.

(a) Bromine (Br2), strontium chloride (SrCl2) and iodine monochloride (ICl) all have similar Mr values.

Suggest, with reasons, the order of melting points for these three substances.(6)

A

SrCl2> ICl > Br>
If wrong can award 1 for one in the correct ‘position’
2
SrCl2 strong ionic bonds / (strong electrostatic attraction between opposite ions)
1
Lattice so many strong bonds to overcome
1
ICl has dipole-dipole between molecules – weaker than ionic bonds
1
Br2 has van der Waals forces between molecules – much weaker
Accept London / dispersion / induced dipole forces

17
Q

Halide ion test for iodide

A

Pale yellow precipitate

18
Q

How can you help differentiate between silver chloride, silver bromide and silver iodide in the halide ion test?

A

The silver halide precipitates can be treated with ammonia solution.

Silver chloride ions dissolve in dilute ammonia to form a colourless solution.

Silver bromide ions dissolve in concentrated ammonia to form a colourless solution.

Silver iodide doesn’t react with ammonia, it is insoluble.

19
Q

What happens to the reducing power of halides as you go down the group ?

A

The reducing power of the halides increases down group 7 They have a greater tendency to donate electrons.
This is because as the ions get bigger it is easier for the outer electrons to be given away as the pull from the nucleus on them becomes smaller.

20
Q

What happens when F- and Cl- react with H2SO4?

A

F- and Cl- ions are not strong enough reducing agents to reduce the S in H2SO4. No redox reactions occur. Only acid-base reactions occur.

21
Q

Write the equation for the reaction of NaF and H2SO4 and what are the observations?

A

NaF (s) + H2SO4(l)—>NaHSO4(s) + HF(g)

Observations: White steamy fumes of HF are evolved.

22
Q

Write the equation for the reaction of NaCl and H2SO4 and what are the observations?

A

NaCl(s) + H2SO4(l)—>NaHSO4(s) + HCl(g)

Observations: White steamy fumes of HCl are evolved

23
Q

Write the 2 steps and the observations of the reaction between NaBr and H2SO4 ?

A

Acids-base step:NaBr(s) + H2SO4(l) —> NaHSO4(s) + HBr(g) Redox step:2HBr+H2SO4 —> Br2(g) + SO2(g) + 2H2O(l)

Observations: White steamy fumes of HBr are evolved.
Red fumes of bromine are also evolved and a colourless, acidic gas SO2

24
Q

Write the 2 half equations for the between reaction NaBr and H2SO4?

A

Ox 1⁄2 equation 2Br- —>Br2 + 2e-

Re 1⁄2 equation H2SO4 +2H+ +2e- —> SO2 +2H2O

25
Q

What is the role of H2SO4 in both steps in the reaction with NaBr?

A

Note the H2SO4 plays the role of acid in the first step producing HBr and then acts as an oxidising agent in the second redox step.

26
Q

What are the 4 reactions when NaI reacts with H2SO4?

A

NaI(s) + H2SO4(l) —> NaHSO4(s) + HI(g)
2HI+H2SO4 —> I2(s) + SO2(g) + 2H2O(l)
6HI+H2SO4 —> 3I2 +S(s)+4H2O(l)
8 HI + H2SO4 —> 4 I2(s) + H2S(g) + 4 H2O(l)

27
Q

What do you observe when NaI reacts with H2SO4?

A

Observations:
White steamy fumes of HI are evolved. Black solid and purple fumes of Iodine are also evolved
A colourless, acidic gas SO2
A yellow solid of sulfur
H2S (Hydrogen sulfide), a gas with a bad egg smell,

28
Q

Define disproportionation.

A

Disproportionation is the name for a reaction where an element simultaneously oxidises and reduces.

29
Q

What is the reaction with Chlorine with water?

A

Chlorine with water:

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

30
Q

What is the reaction of chlorine and water under the presence of UV?

A

Reaction with water in sunlight
If the chlorine is bubbled through water in the presence of bright sunlight a different reaction occurs.
2Cl2 + 2H2O —> 4H+ + 4Cl- + O2
The same reaction occurs to an equilibrium mixture of chlorine water when standing in sunlight. The greenish colour of chlorine water fades as the Cl2 reacts and a colourless gas (O2) is produced.

31
Q

What is the use of chlorine?

A

Chlorine is used in water treatment to kill bacteria. It has been used to treat drinking water and the water in swimming pools. The benefits to health of water treatment by chlorine outweigh its toxic effects.

32
Q

What do you observe when Cl2, Br2 and I2 in aqueous solutions react with Cold Sodium Hydroxide ?

A

The colour of the halogen solution will fade to colourless.

33
Q

What is the equation for the reaction between chlorine and sodium hydroxide?
What is the use for the products?

A

Cl2 (aq) + 2 NaOH (aq) —> NaCl (aq) + NaClO (aq) + H2O (l)

The mixture of NaCl and NaClO is used as bleach and to disinfect/ kill bacteria.

34
Q

What is the Formula for sodium chlorate(I)

A

NaClO

35
Q

What is the formula for sodium chlorate(V) ?

A

NaClO3

36
Q

What is the formula for potassium sulfate(VI) ?

A

K2SO4

37
Q

What is the formula for potassium sulfate(IV) ?

A

K2SO3

Inorganic Chemistry (5 decks)

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