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Chemistry > 3.1.3: The Halogens > Flashcards

3.1.3: The Halogens Flashcards

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1
Q

What colour and state is iodine ?

A

Grey solid

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2
Q

What colour and state is bromine ?

A

Brown-orange liquid

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3
Q

What colour and state is chlorine ?

A

Pale green gas

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4
Q

What colour is fluorine ?

A

Pale yellow gas

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5
Q

Give 2 alternatives to using chlorine for water treatment

A

-Ozone which is a powerful oxidising agent to kill microorganisms but short half life so not permanent and is also expensive
-UV light which damages DNA in microorganisms but is ineffective in cloudy water

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6
Q

Give test for chlorine water

A

Litmus turns red then decolourises

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7
Q

What happens to boiling points down group 7 ?

A

Increases down group as number of electrons increases so more/stronger London forces . more energy to break intermolecular forces

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8
Q

What happens to electronegativity as you go down group 7 ?

A
  • Decreases as atomic radius increases
  • more shielding
  • distance between positive nucleus and bonding electrons increases
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9
Q

Give the 2 main
disadvantages of using chlorine to purify water

A
  • Chlorine is toxic and can form carcinogens or halogenated hydrocarbons
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10
Q

What happens to the reactivity/oxidising power down group 7 ?

A
  • Decreases AND OXIDISING POWER DECREASES
  • atomic radius increases
  • MORE shielding
  • ability to gain electron decreases (ionisation energy)
  • less nuclear attraction
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11
Q

What is the formula for bleach ?

A

HOCl

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12
Q

What type of reaction is a halogen reaction with water ?

A

Disproportionation

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13
Q

Give the equation to form bleach (reaction of halogen with an alkali)

A

2NaOH (aq) + Cl2 (g) = NaCl (aq) + NaOCL (aq) + H2O (l)

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14
Q

Give the formula to show how chlorine is used in water treatment

A

H20 (l) + Cl2 (g) reversible HCl (aq) + HClO

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15
Q

Give 2 benefits of using chlorine in water treatment

A
  • Destroys microorganisms that cause disease
  • Long lasting so reduces bacteria build up
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16
Q

Give 3 disadvantages of using chlorine in water treatment

A
  • Chlorine gas is toxic to respiratory system
  • Liquid chlorine can cause severe skin chemical burns
  • ‘Forced medication on population’
17
Q

What can you use to distinguish between chlorine,bromine and iodine water ?

A

Cyclohexane or an organic solvent that halogens are soluble in and hexane which allows a colour change to be detected. More reactive halogens displace less reactive ones

18
Q

What happens at the same time as reactivity decreases down group 7 ?

A

Oxidising power decreases

19
Q

Give the ionic equation where iodine is displaced by bromine

A

Br2 + 2I- = 2Br- +I2

20
Q

What are the conditions needed for the formation of bleach ?

A

Cold and dilute sodium hydroxide

21
Q

Name apparatus used to separate 2 liquid layers

A

Separating funnel

22
Q

What happens to bond enthalpies down group 7 ?

A

Bond enthalpy decreases C−Cl > C−Br >
C−I

23
Q

How could an experiment be modified so it is completed with ions being produced in less time ?

A

Heat the test tube in a water bath

24
Q

Write an ionic equation for the displacement of iodine by bromine

A

Br2 + 2I– → 2Br– + I2

25
Q

If chlorine displaces another element what can it be described as ?

A

A stronger oxidising agent

26
Q

Give the colour change in cyclohexane if bromine is formed

A

Orange as bromine forms

27
Q

Give the colour of cyclohexane if iodine is formed

A

Lilacas iodine forms

28
Q

What would be observed if chlorine gas is bubbled through aqueas potassium iodide

A

Solution turns brown as iodine forms

29
Q

What would be observed if chlorine gas is bubbled through aqueas potassium bromide

A

Solution turns yellow as bromine forms

30
Q

What would be observed when bromine and potassium iodide are mixed ?

A

Solution turns brown as iodine forms

31
Q

Give ionic equation for bubbling chlorine gas through aqueas potassium iodide

A

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

32
Q

Explain why scientists may be concerned with the presence of chlorine compounds in drinking water ?

A

CHLORINE COMPOUNDS are toxic

33
Q

What are the products formed when sodium hydroxide reacts with hot concentrated sodium hydroxide ?

A

NaClO3 + H20 + Nacl

34
Q

Give a use of NaClO

A

Disinfectant

Chemistry (33 decks)

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