Group 7 Flashcards
What are the Halogens? (fluorine, chlorine, iodine)
Reactive non-metallic elements of the p-block
what is the definition of volatility?
How easily a substance turns from a liquid into a gas
what happens to volatility as you go down the group?
The elements become less volatile as you go down the group
what happens to intermolecular forces as we descend group 7?
The intermolecular forces between the molecules of the halogens increases
what happens to induced dipole dipole interactions as you go down the group?
-they increase due to the molecules containing more electrons
-More energy is required to break the induced interactions between the molecules
what is the bond type in the halogen molecule?
Covalent
What do you halogens exist as?
Diatomic molecules
What is the structure of the halogens?
Simple molecular
what happens to boiling point as you go down the group? (7)
Increases
What happens to the intensity of the colour of the halogens, as you go down the group?
Increases
why would astatine be expected to react similarly to other halogens?
-they all have similar properties
What happens to an oxidising agent?
Gets reduced
what does a halogen atom readily accept an electron to form?
-a halide ion with a full outer shell of electrons (this is a stable arrangement)
what do all halogens act as?
oxidising agents
what is the most powerful oxidising agent?
fluorine
what happens to oxidising power as you go down group 7?
-• (No. of protons/nuclear charge increases down the group but is
outweighed by:)
• Atomic radius increases down the group
• Shielding increases down the group
• Nuclear attraction decreases down the group
• Therefore – it becomes more difficult to gain electron and ability to
oxidise decreases down the group
what colour is produced when chlorine is placed in an aqueous solution?
pale green
what colour is produced when bromine is placed in an aqueous solution?
orange
what colour is produced when iodine is placed in an aqueous solution?
brown
what colour is produced when chlorine is placed in an organic solvent ?
pale green
what colour is produced when bromine is placed in an organic solvent?
orange/brown
what colour is produced when iodine is placed in an organic solvent ?
purple
What is the displacement reaction?
reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions
What can the decrease in the reactivity of the elements as you go down the group be demonstrated by?
-Displacement reactions of aqueous halides using chlorine, bromine and iodine
What are all the types of demonstration observations?
chlorine water, bromine water, and iodine solution with chloride ions, bromide ions and iodide ions
what is the demonstration observation between chlorine water and chloride ions?
No change
what is the demonstration observation between chlorine water and bromide ions?
orange
what is the demonstration observation between chlorine water and iodide ions?
brown
what is the demonstration observation between bromine water and chloride ions?
Orange
what is the demonstration observation between bromine water and bromide ions?
No change
what is the demonstration observation between bromine water and iodide ions?
Brown
what is the demonstration observation between iodine solution and chloride ions?
Stays brown
what is the demonstration observation between iodine solution and bromide ions?
Stays brown
what is the demonstration observation between iodine solution and iodide ions?
No change
what happens when organic solvent (such as cyclohexane) is added to aqueous halogens?
The molecules are extracted into the organic layer (the top) and a more vivid colour is present
in organic solvents like pentane and cyclohexane what colour is iodine?
Violet/purple colour
what colour is iodine in aqueous solution?
brown
when with the organic layer of iodine be pale green?
if it was added to chlorine water on its own
what does chlorine look like when an organic solvent is added to it?
-Organic layer (organic solution) is colourless /green
-Aqueous layer (water solution) colourless /green
what does bromine look like when an organic solvent is added to it?
-organic layer (organic solution) is orange
-Aqueous layer (water solution) is orange
what does iodine look like when an organic solvent is added to it?
-organic layer (organic solution) is purple
-aqueous layer (water solution) is brown
what are organic solvents?
hydrocarbon liquids
what happens when chlorine is added (bubbled) through a solution of potassium iodide?
(worked example of chlorine with iodide)
The aqueous solution becomes brown due to the formation of iodine
What is the ionic equation of chlorine with iodide?
Cl2 (g) + 2l- (aq)—> 2Cl- (aq) + I2 (aq)
(same for bromine with iodide- replace chlorine)
what happens to iodide when it reacts with chlorine?
It is oxidised to iodine
what happens to chlorine when it reacts with iodide?
It is reduced to chloride
why is chlorine oxidising agent in the reaction of chlorine with iodide?
It allows the iodide to be oxidised, itself is reduced
what happens when bromine is added to a solution of potassium iodide?
-The iodide ion has been oxidised to iodine (forming a brown solution) bromine is being reduced to bromide
what happens when chlorine is added to a solution of potassium bromide?
-the aqueous solution becomes orange as bromine is formed
what is the reaction between chlorine with bromide show?
Chlorine is a better oxidising agent than bromine
what does the reactions of bromine and chlorine with iodine show?
-Has been oxidised to iodine
-Chlorine and bromine are stronger, oxidising agents than iodine
-Iodine being the weakest oxidising agent could not displace any of the others from the solutions
in the displacement reactions, what doesn’t have to be considered?
-The metal does not have to be considered as it is a spectator ion
(potassium iodide/bromide)
what is the difference between chloride and chlorine?
chloride=cl-
chlorine=cl2
what happens in the reaction of chlorine with bromide ions?
-Pale green solution turns orange
-on addition of organic solvent, solution turns red
what happens in the reaction of chlorine and iodide ions?
-Pale green solution turns brown
-on addition of organic solvent, solution turns purple
what happened in the reaction of bromine with iodide ions?
-Orange solution turns brown
-on addition of organic solvent, solution turns purple
in the reaction of chlorine with bromide and iodide, why is chlorine the best oxidising agent?
It oxidises both bromide and iodide
In the reaction of iodide with chlorine and bromine, why is iodide the best reducing agent?
It reduces both chlorine and bromine
What is the full balanced equation for the reaction of sodium iodide and bromine?
2Nacl(aq)+Br2(aq) —>2NaBr(aq)+I2(aq)
What is the ionic equation for the reaction of sodium iodide and bromine?
2I- (aq) + Br (aq) —> 2Br- (aq) + I2 (aq)
What is the are the half equations for the reaction of sodium iodide and bromine?
Oxidation: 2I- (aq) —> I2 (aq) + 2e-
Reduction: Br2 (aq) + 2e- —> 2Br- (aq)
What is disproportionation?
when an element is being both oxidised and reduced in a reaction
what happens when chlorine, bromine and iodine are mixed with alkali?
They disproportionate
what is the equation for the reaction between sodium hydroxide and chlorine (example of disproportionation)? (important)
Cl2 (aq) + 2 NaOH (aq) → NaClO (aq) + NaCl (aq) + H2O (l)
what is the condition of the disproportionation reaction of sodium hydroxide and chlorine? (important)
-cold dilute alkali
what does the disproportionation reaction between sodium and chlorine give?
Chloride and chlorate ions, which are present in bleach.
What is the ionic equation for the disproportionation of chlorine?
Cl2 (g) + 2OH- (aq) —> Cl- (aq) + ClO- (aq) + H2O (l)
What do ionic equations balance in terms of?
Chemical species and charge
what is the reaction of chlorine with water used in?
Water Purification
what occurs when chlorine reacts with water?
Disproportionation reaction occurs
what is formed when chlorine reacts with water?
Hydrochloric acid and chloric (I) acid performed
what does the chlorate ion (OCl-) do?
-Kills bacteria as it acts as a weak bleach
How can the acidic nature and the bleaching effect of chlorine and water be seen?
by adding Blue Litmus indicator into aqueous chlorine
what happens to the blue litmus indicator when added into aqueous chlorine?
Blue litmus indicator will turn red (due to the acid) then colourless (due to the bleach)
Why do some people think we should not put chlorine and drinking water?
-chlorine is toxic and excess
-Chlorine to react with hydrocarbons to form chlorinated hydrocarbons with carcinogens
what does the V mean in the name of the sodium compound with the systemic name sodium chlorate (V)?
The chlorine has an oxidation state of +5
what is the overall equation for the reaction of iodine with dilute sodium hydroxide at 25°C?
I2 (aq) + 2NaOH- (aq) —> NaIO (aq) + NaI (aq) + H29 (l)
what is the ionic equation for the reaction of iodine with dilute sodium hydroxide at 25°C?
I2 (aq) + 2OH- (aq) —> IO- (aq) + I- (aq) + H2O (l)
