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Chemistry Year 13 > 1.7- The halogens KEY REACTIONS > Flashcards

1.7- The halogens KEY REACTIONS Flashcards

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1
Q

Colour and state of F Cl Br I and At at room temp and pressure

A

F- pale yellow gas
Cl- pale green gas
Br- red-brown liquid
I- grey-black solid
At- grey-black solid

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2
Q

Explain the increase in boiling point down the group

A

There are more electrons as you go down the halogens, increased number of electrons means increased Van Der Waals’ forces of attraction between atoms, This requires a higher amount of energy to break

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3
Q

Explain the decrease in reactivity down the group

A

In order for a halogen to react they must gain an electron, further down the group the outer shell is further from the positive nucleus so the attraction is weaker, there are also more shielding shells

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4
Q

What colour is iodine vapour?

A

Violet

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5
Q

Describe the colour of chlorine, bromine and iodine when dissolved in water

A

Chlorine- colourless solution
Bromine- Orange solution
Iodine - Brown solution

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6
Q

Describe the colour of chlorine bromine and iodine when dissolved in hexane

A

Chlorine- colourless
Bromine- red solution
Iodine - violet solution

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7
Q

Write an equation for the reaction of chlorine with water

A

Cl2 + H2O -> HOCl + HCl

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8
Q

Write an equation ( and ionic equation ) for chlorine reacting with COLD DILUE sodium hydroxide SOLUTION

A

Cl2 + 2NaOH -> NaCl + NaClO + H2O
Cl2 + 2OH- -> Cl- + ClO- + H2O

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9
Q

What is the name of NaClO

A

Sodium hypochlorite

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10
Q

Write an equation ( and ionic equation ) for the reaction of chlorine with HOT CONCENTRATED sodium hydroxide SOLUTION

A

3Cl2 + 6NaOH -> 5NaCl + NaClO3 + 3H2O

3Cl2 + 6OH- -> 5Cl- + ClO3- + 3H2O

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11
Q

What is the name of NaClO3

A

Sodium chlorate(V)

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12
Q

What is the typical colour change in a halogen displacement reaction

A

Colourless -> colour of displaced ion in solution

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13
Q

Describe why the reducing ability of the halide ions increases as you descend the group

A

Deducting agents are electron donors
As you descend the group the outer electrons are further from the positive nucleus and also more shielded so the attraction to the nucleus is weaker as you descend the halides

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14
Q

Reaction of fluoride with conc. sulfuric acid, state any observations

A

NaF + H2SO4 -> NaHSO4 + HF

Misty fumes ( HF ) heat released, gas produced, solid disappears, pungent smell ( HF )
Products: Sodium Hydrogensulfate and hydrogen fluoride

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15
Q

Reaction of Chloride with concentrated sulfuric acid, state any observations

A

NaCl + H2SO4 -> NaHSO4 + HCl
* Not Redox *
Misty fumes ( HCl ), heat released, gas produced, solid disappears, pungent smell ( HCl)
Products: Sodium Hydrogensulfate and sodium chloride

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16
Q

Reaction of Bromide with concentrated sulfuric acid, state any observations

A

NaBr + H2SO4 -> NaHSO4 + HBr
2HBr + H2SO4 -> Br2 + SO2 + 2H2O
Observations: misty fumes ( HBr ), heat released, gas produced, solid disappears, red-brown vapour ( Br2 ), Pungent smell (HBr/SO2/Br2
Products: sodium hydrogensulfate, hydrogen bromide, bromine, water, sulfur dioxide

17
Q

Reaction of iodide with concentrated sulfuric acid, state any observations

A

NaI + H2SO4 -> NaHSO4 + HI
2HI + H2SO4 -> SO2 + I2 + 2H2O
6HI + H2SO4 -> S + 3I2 + 4H2O
8HI + H2SO4 -> H2S + 4I2 + 4H2O

Observations: misty fumes (HI) heat released, gas produced, solid disappears, purple vapour, grey black solid formed(I2), pungent smell ( HI/SO2/I2), rotten eggs smell (H2S), yellow solid (S)

Products: sodium hydrogensulfate, hydrogen iodide, iodine, sulfur dioxide, sulfur, hydorgen sulfide, water

18
Q

Write an equation for the reaction of halides with phosphoric acid

A

NaF + H3PO4 -> NaH2PO4 + HF
KI + H3PO4 -> KH2PO4 + HI

All halides react the same way as they can’t reduce phosphoric acid
Forms a dihydrogenphosphate salt

19
Q

What is Ozone and how can it be generated

A

Ozone is an allotrope of oxygen, O3
It’s generated by passing a high voltage electric discharge through oxygen
OR using UV light 3O2 -> 2O3

20
Q

How do ozone and hypochlorous acid kill microorganisms

A

They oxidise them

21
Q

Advantages of treating water with chlorine

A

Cheaper than ozone
Provides residual protection as it’s still present until reaches the consumer
More soluble in water than ozone

22
Q

Disadvantages of treating water with chlorine

A

Cannot kill all microorganisms
Leaves chemicals in the water
Unpleasant taste
Toxic to humans

23
Q

Advantages of treating water with ozone

A

Kills more types of microorganisms than chlorine
Breakdown product is oxygen
No residual chemicals
Removes metal and organic particles
No unpleasant taste

24
Q

Disadvantages of treating water with ozone

A

More expensive than chlorine
Does not provide residual protection
Less soluble than chlorine so requires special mixing technique

Chemistry Year 13 (10 decks)

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