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A Level Chemistry > GROUP 7 > Flashcards

GROUP 7 Flashcards

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1
Q

What is the appearance of fluorine?

A

pale yellow gas

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2
Q

What is the appearance of chlorine?

A

green gas

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3
Q

What is the appearance of bromine?

A

red-brown liquid

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4
Q

What is the appearance of iodine?

A

grey solid

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5
Q

Trend in boiling points down the group? Why?

A

INCREASE
Increasing strenght of the VDW forces as the size and relative mass of the molecules increases

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6
Q

Trend in electronegativity down the group? Why?

A

DECREASES
Smaller atoms are better at attracting electrons
Larger atoms are weaker at attracting electrons than smaller atoms
Because their outer electrons are further from the nucleus and are more shielded as they have more inner electrons

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7
Q

What halogens react, what happens?

A

They gain an electron

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8
Q

How do halogens act when they react?

A

They act as oxidising agents

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9
Q

What happens to reactivity down the group and what does this mean for their oxidising ability?

A

Less reactive down the group as atoms become larger and outer electrons become further from the nucleus
HALOGENS BECOME LESS OXIDISNG DOWN THE GROUP

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10
Q

Trend in oxidising ability of halogens down the group?

A

Weaker oxiding ability as you go down the group as the atoms get bigger

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11
Q

What happens during a halogen displacement reaction? Give an example:

A

A halogen will displace a halide from solution if the halide is below the halogen in the periodic table
e.g. chlorine could displace bromide ions)

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12
Q

How do you carry out a halogen displacement reaction?

A

Add a few drops of an aqueous halogen to a solution containing halide ions. A colour change will be seen if there is a reaction

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13
Q

Chlorine water (colourless) +KCl

A

no reaction

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14
Q

Chlorine water (colourless) + KBr

A

orange solution formed as Br2 forms because chlorine displaced the Br from KBr

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15
Q

Chlorine water (colourless) + KI

A

brown solution of I2 formed

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16
Q

Bromine water (orange) + KCl

A

no reaction

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17
Q

Bromine water (orange) + KBr

A

no reaction

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18
Q

Bromine water (orange) + + KI

A

brown solution of I2 formed

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19
Q

Iodine solution (brown) + KCl

A

no reaction

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20
Q

Bromine water (orange) + KBr

A

no reaction

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21
Q

Bromine water (orange) + KI

A

no reaction

22
Q

What colour are halides in solution?

A

COLOURLESS IN SOLUTION

23
Q

What changes to help us identify which halogen/halide is present in solution? Give an example

A

A colour change
e.g. when bromide ions come out of solution to form bromine there is a colour change from colourless to orange

24
Q

Why don’t we need to know about fluorine in displacement reactions?

A

Because it oxidises the water instead of forming a solution

25
Q

What is the proper name for bleach?

A

sodium chlorate(I) solution
NaClO(aq)

26
Q

How do we get bleach?

A

Mix chlorine gas with cold, dilute sodium hydroxide solution at room temp

27
Q

What type of reaction takes place when forming bleach? Why?

A

Disproportionation reaction as chlorine is both oxidised and reduced

28
Q

What is the reaction for the formation of sodium chlorate(I)
/bleach?

A

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

29
Q

When you mix chlorine with water, what happens? Type of reaction?

A

You get a disproportionation reaction and you end up with a mixture of chloride ions and chlorate(I) ions

30
Q

What is the equation for the reaction between chlorine and water?

A

Cl2(g) + H2O(l) <–> (reversible) 2H+(aq) + Cl-(aq) + ClO-(aq)

31
Q

What is the equation for the reaction between chlorine and water IN SUNLIGHT?

A

Cl2(g) + H2O(l) <–> 2H+(aq) + 2Cl-(aq) + 1/2O2(g)

32
Q

How does chlorine help in water treatment?

A

Chlorate (I) ions kill bacteria. So adding chlorine to water can make it safe to drink/swim in.

33
Q

How does chlorine help make our water safe?

A

kills disease-causing microorganisms
prevents growth of algae
removes discolouration caused by organic compounds

34
Q

What are the risks for using chlorine to treat water?

A

Chlorine gas is very harmful if it is breathed in
Liquid chlorine on skin/eyes causes severe chemical burns
Chlorine can also react with the organic compounds found in water to form chlorinated hydrocarbons (e.g chloromethane)
Many of which are carcinogenic
However benefits outweigh risks

35
Q

What do HALIDE IONS act as?

A

reducing agents and are oxidised themselves

36
Q

For a halide ion to reduce something, what needs to happen?

A

the halide ion needs to lose an electron from its outer shell

37
Q

What is the trend in the reducing power of halides as you go down the group?

A

INCREASES down the group

38
Q

Explain the trend in the reducing power of halides as you go down the group:

A

It increases because the halide ions are increasing in size as there are more electrons so there is more shielding which means there is a weaker attraction between the nucleus and the outer electrons so they can be lost easier.

39
Q

All halides react with conc sulfuric acid to give what?

A

A hydrogen halide

40
Q

Equation for the reaction between conc sulfuric acid and a sodium halide using ‘X’ to represent the halide:

A

NaX + H2SO4 –> NaHSO4 + HX

41
Q

What is the overall reaction between a sodium halide and conc sulphuric acid IF you have a strong enough halide?

A

2HX + H2SO4 –> SO2 + X2 + 2H2O

42
Q

What are the half equations when conc sulfuric acid reacts with a sodium halide?

A

2X- (g) –> X2(s) + 2e- (Halide is oxidised)
H2SO4 + 2H+ +2e- –> SO2(g) + 2H2O(l) (Sulfuric acid reduced)

43
Q

What can iodine do during the reaction between a sodim halide and conc H2SO4 and why?

A

Iodine is such a strong reducing agent that it can actually reduce the SO2 to H2S or S.

44
Q

What is the equation for the reaction between NaF and conc H2SO4?

A

NaF(s) +H2SO4(l) –> NaHSO4(s) + HF(g)
NOT REDOX REACTION
MISTY FUMES

45
Q

What is the equation for the reaction between NaCl and conc H2SO4?

A

NaCl(s) + H2SO4(l) –> NaHSO4(s) + HCl(g)
NOT REDOX REACTION
MISTY FUMES

46
Q

What is the equation for the reaction between NaBr and conc H2SO4?

A

NaBr(s) + H2SO4(l) –> NaHSO4(s) +HBr(g)
MISTY FUMES

47
Q

Give the equation for the redox reaction between HBr and H2SO4?

A

2HBr(g) +H2SO4(l) –> Br2(g) + SO2(g) + 2H2O(l)
CHOKING FUMES OF SO2
ORANGE FUMES OF BR2

48
Q

What is the equation for the reaction between NaI and conc H2SO4?

A

NaI(s) + H2SO4(l) –> NaHSO4(s) + HI(g)

49
Q

Give the equation for the redox reaction between HI and H2SO4?
Where h2so4 is reduced by HI

A

2HI(g) + H2SO4(l) –> SO2(g) + I2(s) + 2H2O(l)
GREY SOLID +/or PURPLE GAS

50
Q

What is the strongest reducing agent of the hydrogen halides?

A

HI

51
Q

What is the final stage of the reaction between NaI and H2SO4?

A

6HI(g) + SO2(g) –> H2S(g) + 3I2(s) + 2H2O(l)
FUMES OF H2S
SOLID IODINE

A Level Chemistry (17 decks)

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