(blue) Halogens Flashcards
(blue) Halogens
what are the gp 7 elements in the periodic table
there called halogens , they are highly reactive , only exsits as compounds in nature
how do gp7 elements for ions
they loose electrons the form halide ions
what type of bond do they most likly form
covalent
propertys of fluorine :
formula of molecule
F2
propertys of fluorine :
Appearance and state at room temp
Pale yellow gas
propertys of fluorine :
Electron
configuration
1s2 2s2 2p5
propertys of fluorine :
Bleaching
ability
Very strong
propertys of fluorine :
Solubility in
water and
appearance of
solution
Reacts with water to form HF and O2
propertys of chlorine :
Formula of
molecule
Cl2
propertys of chlorine :
Appearance
and state at
room temp
Green/yellow gas
propertys of chlorine :
Electron
configuration
1s2 2s2 2p6 3s2 3p5
propertys of chlorine :
Bleaching
ability
Strong
propertys of chlorine :
Test for the gas
Damp blue litmus paper Turns red then bleached Or Damp starch iodide paper Turns blue
propertys of chlorine :
Solubility in
water and
appearance of
solution
Slight solubility but also reacts to form chlorine water HCl and HOCl Pale green soln.
Trend in
solubility in
H2O of Cl2 to I2
decreses in solubnility
propertys of chlorine :
Solubility in
cyclohexane
and appearance
of solution
Soluble Yellow/green solution
propertys of bromine :
Formula of
molecule
Br2
propertys of bromine :
Appearance
and state at
room temp
Dark red/brown liquid
propertys of bromine :
Bleaching
ability
Weak
propertys of bromine :
Test for the gas
Damp starch + iodide paper Turns blue Bubble through KI solution with starch
propertys of bromine :
Solubility in
water and
appearance of
solution
Slight solubility but also reacts to form bromine water HBr and HOBr Orange solution
propertys of bromine :
Solubility in
cyclohexane
and appearance
of solution
Soluble red solution
propertys of iodine :
Formula of
molecule
I2
propertys of iodine :
Appearance
and state at
room temp
Shiny grey solid
propertys of iodine :
Electron
configuration
[Kr] 5s2 4d10 5p5
propertys of bromine :
Electron
configuration
[Ar] 4s2 3d10 4p5
propertys of iodine :
Bleaching
ability
none
propertys of iodine :
Test for the gas
Starch solution turns blue/black
propertys of iodine :
Solubility in
water and
appearance of
solution
Almost insoluble producing a very pale brown solution. Soluble in KI solution à dark brown solution.
propertys of iodine :
Solubility in
cyclohexane
and appearance
of solution
Soluble purple solution
describe the general trend in bleaching ability down the halogens
gets weaker
describe the general trend solubility on water down the group for halogens
F2 soluable , however rest is all silightly soluable
State, and explain the change in melting pts down .group 7
Increases, as the number of electrons increases the London forces also increase (IMF) requiring more energy to overcome.
State and explain the change in electronegativity down group 7.
Decreases, outer electrons are progressively more shielded from the nucleus as the atomic radius increases, also the distance between the bonding pair and nucleus increaces. (proton number increaes but this is more than offset by the other factors) So electrons in a covalent bond are attracted less to the halogen.
State and explain the change in reactivity of the Group 7 elements down group 7
As most reactions with halogens result in the halogen gaining an electron. They become less reactive on descending. Reactivity decreases as atomic radius increases and more shielding means electrons attracted less strongly to the nucleus.
What is the problem in distinguishing between bromine and iodine solutions?
Depending on concentration both could appear a brown/orange colour.
How could you show that you have a solution of iodine? Give two methods.
· Add an organic solvent and shake. Halogens are more soluble in organic solvents, Iodine —-> purple colour in upper, organic layer, bromine —-> red organic layer
· Add starch solution and shake. Iodine —->blue / black.
how would you seperate bromine from iodine in a seperating funnel
add organinc solvent e.g hexane
shake and allow to settle
iodine moves to hexane layer
open tap and run off iodine layer
most metals react with halogens to make what
ionic compounds
Mg(s) + Cl2(g) —–> MgCl2(s)
which one has been oxidised and which has been reduced
What has been oxidised :Magnesium
What has been reduced? chlorine
when Cl , br and I react with AL to what charge does AL get oxidised to
Al —-> Al 3+ + 3e -
aluminium + bromine
what are the :
Observations
Oxidation equation
Reduction equation
Bromine liquid dropped on Aluminium foil. Sparks and glowed red Got hot and a lot of bromine vapour evolved. A white solid remained.
Oxidation equation Al(s) —–> Al3+ + 3e-
Reduction equation Br2 + 2e- —-> 2Br-
aluminium + iodine:
what are the :
Observations
Oxidation equation
Reduction equation
Vigorous reaction, clouds of purple I2vapour. Solid glowed red-hot Grey solid AlI3 remaine
Oxidation equation : Al(s) —-> Al3+ + 3e-
Reduction equation: I2 + 2e- ——> 2I-
how do halogens oxidise Fe 2+
Fe 2+ goes to Fe 3+
halogens are also reduced to halide ions
what is the Observation on adding Fe2+ to Cl2
also what is the reduction , oxi and redox reaction
Solution became very pale yellow (thiocyanate —-> red therefore Fe3+ present)
reduction : Cl2 + 2e- —-> 2Cl-
oxi : Fe2+—–> Fe3+ + e-
redox Cl2 + 2Fe2+ —–> 2Fe3+ + 2Cl-
what is the Observation on adding Fe2+ to Br2
also what is the reduction , oxi and redox reaction
Solution became very pale yellow (thiocyanate ——> red therefore Fe3+ present)
reduction : Br2 + 2e- —–> 2Br-
oxi : Fe2+ ——> Fe3+ + e-
redox : Br2 + 2Fe2+ ——> 2Fe3+ + 2Br-
what is the Observation on adding Fe2+ to I2
also what is the reduction , oxi and redox reaction
No change (thiocyanate ——-> unchanged - no Fe3+)
reduction + oxi + redox : none as no reaction
what is a test to test for Fe 3+
Additional test for Fe3+ = add potassium thiocyanate (KSCN) a red colour indicates Fe3+
what is the colour of KCl
colourless solution
what is the colour of KBr
colourless solution
what is the colour of KI
colourless solution
what happens when you mix
chlorine with KCl
nothing
as Cl cannot oxidise its self
what happens when you mix
chlorine with KBr
colourless solution turns pale yellow
hexane —-> red
this is because Cl oxidises the Br
what happens when you mix
chlorine KI
colourless solution turn orange brown
henane —-> purple
this is because Cl oxidises the Br
what happens when you mix
bromine with chlorine
just a dilution of the orange colour
Br cannot oxidise Cl
what happens when you mix
bromine with Br
nothing as Br cannot oxidise its self
what happens when you mix
bromine with KI
turned dark orange ,
starch —-> blue/black
Br can oxidise I from KI
what happens when you mix
iodine with KCl / KBr /KI
nothing there will just be a dilution of the origonal colour as iodine cannot oxidise any of the halide ions
Does chlorine (Cl2) oxidise
Br- (aq)
I- (aq)
yes
yes
Does bromine (Br2) oxidise
Cl- (aq)
I- (aq)
no for Cl
yes for I