Module 3 - Halogens Flashcards

1
Q

What group elements are
referred to as halogens?

A

7

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2
Q

List 2 properties of halogens

A

● Low melting and boiling points
● Exist as diatomic molecules

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3
Q

What is the trend in boiling
point down group 7? Why?

A

Increases down the group because:
-size of atom increases as more occupied electron shells →
stronger London forces of attraction between molecules, take
more energy to break

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4
Q

What is the trend in reactivity
down group 7? Why?

A

Reactivity decreases because:
● Atomic radius increases
● Electron shielding increases
● Ability to gain an electron and form 1- ions
decreases

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5
Q

What is the trend in oxidising
ability down the group? Why?

A

Decreases down group (Cl strongest, I weakest)
This is because Cl has the fewest occupied electron shells,
greatest force of attraction between outer electrons and
nucleus and thus is the easiest to gain electrons and be
reduced → best oxidising agent

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6
Q

What is the trend in reducing
ability of the halides down the
group? Why?

A

Increases down the group (Cl- weakest, I- strongest)
This is because I- has the most occupied electron shell so
outer electrons are further from the nucleus, weakest force of
attraction between outer electrons and positive charge of
nucleus and thus is the easiest to be oxidised and lose
electrons → best reducing agent

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7
Q

When a more reactive halogen
displaces a less reactive
halide, what is the reaction
called?

A

Displacement reaction

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8
Q

What is the colour of chlorine
in water?

A

pale green

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9
Q

What is the colour of bromine
in water?

A

orange

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10
Q

What is the colour of iodine in
water?

A

brown

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11
Q

What is the colour of chlorine
in cyclohexane?

A

pale green

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12
Q

What is the colour of bromine
in cyclohexane?

A

orange

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13
Q

What is the colour of iodine in
cyclohexane?

A

violet

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14
Q

Out of the 3 halides Cl- , Br-
& I- , which one of these can be
oxidised by chlorine?

A

Br- & I-
ions

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15
Q

Write the equation for chlorine
oxidising bromide ions

A

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

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16
Q

Write the equation for Cl2
oxidising 2I?

A

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

17
Q

Out of the 3 halides Cl- , Br- &
I- , which one of these can be
oxidised by bromine?

A

I- ions

18
Q

Write the equation for bromine
oxidising iodide ions

A

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

19
Q

Out of the 3 halides Cl- , Br- &
I- , which one of these can be
oxidised by iodine?

A

Does not oxidise Cl-
or Br-

20
Q

Define disproportionation

A

The oxidation and reduction of the same
element in a redox reaction

21
Q

What is the equation for the
reaction of Cl2
with water?

A

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

22
Q

What type of reaction is the
reaction of chlorine with
water?

A

Disproportionation; chlorine is both
oxidised and reduced

23
Q

Why is chlorine added to
drinking water?

A

It kills the bacteria in the water and
makes it safer to drink

24
Q

What are the two forms of the
chlorate ion?

A

ClO- is chlorate (I)
ClO₃- is chlorate (V)

25
Q

What is the equation for
forming bleach?

A

Cl₂ (aq) + 2NaOH (aq) → NaCl (aq) +
NaClO (aq) + H₂O (l)
NaClO is bleach