Group 7 Flashcards
Group 7 elements are
non metals and very reactive
they react with metals to form salts
Group 7 element are all
very reactive non metals and known as halogens but exist as ions n are instead known as hallowed
at room temperature what does fluorine form?
at room temperature fluorine is a gas
and forms a pale yellow colour
at room temperature what does chlorine form
at room temperature chlorine si a gas and forms a pale green colour
at room temperature what does bromine form
at room temperature bromine is a liquid with red brown or red brown colour
at room temperature what does iodine form
iodine forms a solid at room temperature and forms a black colour
As we go down group 7 electronegativity
decreases
Why does electronegativity decrease down a group
there are more full shells of electrons
there is a greater shielding of outer
electrons
atomic radius increases
and the distances between nucleus and the shared electron pair increases
State the trend in the boiling points of the halogens from fluorine to iodine and explain this trend
boiling point increases from fluorine to iodine
this is because the molecule increase in size/molecular mass/ surface area/ number of electrons
this increases the strength of van der waals forces between molecules
therefore more energy is needed to overcome these forces
Halogens can act as a oxidising agent what is the most oxidising agents
fluorine and therefore displaces chloride bromide and iodide ions
whilst chlorine displaces bromide and iodide but not fluoride ions
bromine is only able to displace iodide ions
so going down a group oxidising ability decreases
The oxidising ability of the halogens d
and the reducing ability of halides
oxidising ability of halogens decrease down a group
and reducing ability of hallides increase down the group
Which reaction takes place between fluoride ions and concentrated sulfuric acid
acid base reaction
which reaction take place between chloride ions and concentrated sulfuric acid
acid base reaction
Bromide ions react with sulfuric acid to produce
an acid base reaction and a redox reaction
producing hydrogen bromide perceived as steamy fumes
and in redox reaction bromine vapour which is perceived as brown colour in the stream fumes
when concentrated sulfuric acid is added to sodium iodide salt we can make several observations & acid base reaction occurs & redox reactions
1) state the chemical formula or the substance which is observed as steamy fumes
2) state the chemical formula to ether substance which is observed as black solid
3) state the chemical formula of the substance which is observed as a yellow solid
4) state the chemical formula of the substance which is observed as the smell of rotten eggs
1) HI (g) (
2) I2 (g)
3) S (s)
4) H2S (g)
what is the name given to a halogen that has gained an electron
halide
under standard conditions halogens exist as
as a molecule containing 2 atoms
the boiling point of the halogens increases doen the group as the number of electrons increases and thus the strength of van der waals forces increases
Which of the following will oxidise iodide ions to iodine?
1) F2
2) Cl2
3) Br2
down the group the ability of shooters to act as an oxidising agent decreases
this makes f2 cl2 br2 stronger oxidising agents than i2
therefore f2 cl2 and br2 will oxidise I- to I2
Complete the balanced half equation for the oxidation of bromide
1) 2Br —>
Br2 + 2e-
complete the balanced half equation for the reduction of fluorine
2) F2 + 2e- —>
2F-
State the overall equation for the oxidation of bromide with fluorine
2Br- + F2 —> Br2 + 2F-
Which half-life is the strongest reducing agent
1) fluoride
2) chloride
3) bromide
4) iodide
Iodide as doen a group hallides reducing power increases
State the acid base reaction when sodium bromide reacts with the concentrated sulfuric acid
complete the following redox reaction equation for bromides reaction with concentrated sulfuric acid
2H+ + 2Br- + H2SO4 (l) —>
2H+ + 2Br- + H2SO4 (l) —> SO2 (g) + 2H2O (l) + Br2 (l)
Silver nitrate react with the different halide ions to form silver hallides
state what would be observed when each of the following forms
silver fluoride -> forms no precipitate
silver chloride -> white precipitate
silver bromide -> creamy precipitate
silver iodide -> pale yellow precipitate
What happens if the aqueous solution contains impurities like hydroxides or carbonates ?
2Ag+ + CO23- —>
Ag+ + OH- —>
Ag2CO3 (s) then silver carbonate would form
AgOH (s) then silver hydroxide would form
since both are insoluble in water it would precipitate and invalidate the test
thow do we remove this to purify the test?
we need to acidify the solution to do this we dilute the solution with nitric acid
which react with any soluble hydroxide to form water and any soluble carbonates to form carbon dioxide and water
How to identify silver hallides ?
after adding silver nitrate into hallides ions we might not be able to tell the precipitates so we need to add dilute ammonia to the solution
silver chloride will dissolve to forms. colourless solution
leaving our 2 finals (Br - and I)
last step is to add concentrated ammonia which makes silver bromide dissolve
leaving silver iodide which is insoluble in any ammonia solvent
An aqueous solution was acidified with dilute hydrochloric, and silver nitrate solution was then added.
A precipitate formed
Dilute ammonia solution was then added to the solution, but the
precipitate did not dissolve.
Concentrated ammonia solution was then added, but the precipitate still
identify the hallide ion in the solution
iodide is the hallide
Why is HClO called chloric (i) acid
because it’s chlorine atom has an oxidation state of 1+
The reaction between chlorine and water is Cl2 (ag) + H2O () = HCI (ag) + HCIO (ag).
Which of the following changes would shift the equilibrium to the left?
A)Increasing the concentration of Cl2 (ag)
B)Increasing the concentration of HC1 (ag)
C)Adding water to the reaction vessel
D) Increasing the pressure
By increasing the concentration of Cl2 and adding water equilibrium would shift to the right
increasing the pressure will not affect equilibrium bcs none of the reacting species are gaseous
the only option left is increasing concentration of HCl
the equilibrium shifts to opposo the change removing the HCl by producing more Cl2 and H2O
The reaction between chlorine and water is Cly (ag) + H, 0 (1) # HCI (ag) + HCIO (ag).
Give the oxidation states of chlorine in the following species:
1) Cl2
2) HCI
3) HCIO
4) This type of reaction is known as a/an
1) 0
2) -1
3) +1
4) known as an disproportionation reaction
When chlorine is first added to pools, a greenish tint forms.
1) This is due to the presence of…
2) Over time the greenish tint disappears. This is due tot he chlorine reacting with water to form…
1) Cl2 / chlorine
2) HCl (aq) + HCIO
Why is HCIO more useful than HCl for sterilising pools?
The bacteria in the water are killed by oxidation using HCIO
Why do outdoor pools require more chlorine to sterilise them than indoor pools?
In the presence of sunlight, chlorine reacts with water to form hydrochloric acid and oxygen, in an irreversible reaction
in outdoor pools, there is brighter sunlight so this reaction happens rapidly
this causes chlorine to be lost from pools meaning less chlorine available to restrict with water to form chloric (I) acid which is the oxidising agent needed to kill bacteria
therefore outdoor pools require more chlorine to sterilise them than indoor pools
Which of the following statements is true about the chlorination of water supplies?
Select all that apply
A) Chlorine is added to help sterilise water supplies.
B) Chlorine levels in tap-water need to be closely monitored.
C) Chlorine is toxic to humans even at very low concentrations.
D) Chlorination can be considered wasteful because most tap-water is not used for drinking.
E) Chlorination has not saved many lives.
A B D
Which of the following species is an oxidising agent?
A) HCIO B) HCl C) NaClO D) NaCl E) H2O
A and C
which of the following is a disproportionation reaction?
B and D
bcs
Is the reaction with chlorine reversible?
the reaction between chlorine and water without sunlight is reversible
Which of the following is a typical example of a use for NaClO (aq)
household bleach to kill bacteria and remove stains
