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F321 Chemistry > Group 7- The Halogens > Flashcards

Group 7- The Halogens Flashcards

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1
Q

What are the first 4 halogens?

A

Flourine
Chlorine
Bromine
Iodine

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2
Q

What are the colours of the first 4 halogens?

A

Fluorine is very pale yellow
Chlorine is yellow-green
Bromine is red-brown
Iodine is grey

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3
Q

What are the physical states of the first 4 halogens?

A

Gas: fluorine and chlorine
Liquid: bromine
Solid: Iodine

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4
Q

What is the trend in boiling and melting points in the first 4 halogens?

A

They increase down the group.
Due to increasing strength of van der Waals forces as the number of electrons increases when the size and relative mass of the atoms increases.

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5
Q

What is produced when halogens are reduced?

A

Hallide ions

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6
Q

What is the trend in reactivity for the first 4 halogens?

A

Reactivity increases down the group as because there is more shielding between the nucleus and the outer electrons and the distance between the nucleus and the outer electron increases and therefore the force of attraction between the nucleus and outer most electrons is reduced. Also, the atomic radius increases, which is due to the extra shell of electrons for each element.

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7
Q

What are the displacement reactions for the chlorine halogen?

A

Chlorine will displace bromine and iodide.

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8
Q

What are the displacement reactions for the bromine halogen?

A

Bromine will displace iodide.

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9
Q

What are the displacement reactions for the iodide?

A

No reaction with fluorine, chlorine or bromine.

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10
Q

When displacement reactions happen, there are colour changes. Sometimes they can look similar, what can be added to make the change in colour easier to see?

A

An organic solvent such as hexane.
The halogen thats resent will dissolve readily in the organic solvent which settles of as a distinct solvent layer above the aqueous solution.

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11
Q

What colour shows the presence of iodine when added to hexane?

A

Violet/pink colour

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12
Q

What colour shows the presence of bromine when added to hexane?

A

Orange/red colour

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13
Q

What colour shows the presence of chlorine when added to hexane?

A

Very pale yellow/green

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14
Q

Describe a chemical test which the student could have carried out to prove that the filtrate
contains aqueous chloride ions.

A

Add (aqueous) silver nitrate

white AND precipitate

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15
Q

What are the group 7 elements known as?

A

The halogens

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16
Q

Ionic equation for chlorine displacing bromine.

A

Cl2 (aq) + 2Br- (aq) -> 2Cl- (aq) + Br2 (aq)

17
Q

Ionic equation for chlorine displacing iodide.

A

Cl2 (aq) + 2I- (aq) -> 2Cl- (aq) + I2 (aq)

18
Q

Ionic equation for bromine displacing iodide.

A

Br2 (aq) + 2I- (aq) -> 2Br- (aq) + I2 (aq)

19
Q

What colour precipitate do you get when you add silver nitrate to fluoride?

A

Fluoride produces no precipitate (silver fluoride is soluble in water)

20
Q

What colour precipitate do you get when you add silver nitrate to chloride?

A

White precipitate

21
Q

What colour precipitate do you get when you add silver nitrate to bromide?

A

Cream precipitate

22
Q

What colour precipitate do you get when you add silver nitrate to iodide?

A

Yellow precipitate

23
Q

To be sure, how do you further identify your results from the silver nitrate test and why?

A

Add ammonia solution.

Each silver halide has a different solubilty in ammonia.

24
Q

What happens when you add ammonia solution to chloride halide?

A

Precipitate dissolves in dilute NH3 (aq)

25
Q

What happens when you add ammonia solution to bromide halide?

A

Precipitate dissolves in CONC NH3 (aq)

26
Q

What happens when you add ammonia solution to iodide halide?

A

Precipitate insoluble in CONC NH3 (aq)

27
Q

What is disproportionation?

A

When a single element is simultaneously oxidised and reduced.
The halogens undergo disproportionation when they react with cold dilute alkali solutions such as NaOH.

28
Q

What is the formula for bleach?

A

NaClO

29
Q

How do you make bleach?

A

Mix chlorine gas with dilute sodium hydroxide at room temperature and you get sodium chlorate (I) solution.

30
Q

What do chlorate ions do?

A

Kill bacteria.

31
Q

What are the risks of using chlorine to treat water?

A

Chlorine gas is toxic.

Harmful if breathed in.

32
Q

Why do we involve chlorine in water treatment?

A

It kills disease causing microorganisms.
Prevents growth of algae, eliminating bad tastes and smells.
It removes decolouration caused by organic compounds.

F321 Chemistry (25 decks)

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