Module 3 - Halogens Flashcards
What group elements are
referred to as halogens?
7
List 2 properties of halogens
● Low melting and boiling points
● Exist as diatomic molecules
What is the trend in boiling
point down group 7? Why?
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
What is the trend in reactivity
down group 7? Why?
Reactivity decreases because:
● Atomic radius increases
● Electron shielding increases
● Ability to gain an electron and form 1- ions
decreases
What is the trend in oxidising
ability down the group? Why?
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
What is the trend in reducing
ability of the halides down the
group? Why?
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
When a more reactive halogen
displaces a less reactive
halide, what is the reaction
called?
Displacement reaction
What is the colour of chlorine
in water?
pale green
What is the colour of bromine
in water?
orange
What is the colour of iodine in
water?
brown
What is the colour of chlorine
in cyclohexane?
pale green
What is the colour of bromine
in cyclohexane?
orange
What is the colour of iodine in
cyclohexane?
violet
Out of the 3 halides Cl- , Br-
& I- , which one of these can be
oxidised by chlorine?
Br- & I-
ions
Write the equation for chlorine
oxidising bromide ions
Cl₂ (aq) + 2Br- (aq) → 2Cl- (aq) + Br₂ (aq)
Write the equation for Cl2
oxidising 2I?
Cl₂ (aq) + 2I- (aq) → 2Cl- (aq) + I₂ (aq)
Out of the 3 halides Cl- , Br- &
I- , which one of these can be
oxidised by bromine?
I- ions
Write the equation for bromine
oxidising iodide ions
Br₂ (aq) + 2I- (aq) → 2Br- (aq) + I₂ (aq)
Out of the 3 halides Cl- , Br- &
I- , which one of these can be
oxidised by iodine?
Does not oxidise Cl-
or Br-
Define disproportionation
The oxidation and reduction of the same
element in a redox reaction
What is the equation for the
reaction of Cl2
with water?
Cl₂ (g) + H₂O (l) → HClO (aq) + HCl (aq)
What type of reaction is the
reaction of chlorine with
water?
Disproportionation; chlorine is both
oxidised and reduced
Why is chlorine added to
drinking water?
It kills the bacteria in the water and
makes it safer to drink
What are the two forms of the
chlorate ion?
ClO- is chlorate (I)
ClO₃- is chlorate (V)
What is the equation for
forming bleach?
Cl₂ (aq) + 2NaOH (aq) → NaCl (aq) +
NaClO (aq) + H₂O (l)
NaClO is bleach
