Group 7 Flashcards
What is the appearance and colour of fluorine(pure, non-polar solvents,water)
Pure=pale yellow gas
Non polar = reacts with solvent (none)
Water=reacts(none)
What is the appearance and colour of chlorine (pure, non-polar solvents,water)
Pure=pale green gas
Non polar=pale green solution
Water=pale green solution
What is the appearance and colour of bromine (pure, non-polar solvents,water)
Pure=dark red liquid
Non polar=orange solution
Water=orange solution
What is the appearance and colour of iodine (pure, non-polar solvents,water)
Pure=grey solid
Non polar=purple solution
Water=insoluble but forms brown solution if excess KI present
Why do mp and bp increase steadily down the group 7?
Increase in vdw due to increased electron and surface area
What happened to oxidising power as you go down the group 7 and why?
Decreases as more number of shells more shielding from nucleus thus weaker attraction to electron they want to accept
What happens to reducing power down the group 7 and why?
It increases ,(fluoride ions have no significant reducing powers)
Number of shells increase , more shielding of nucleus outer electron become less attracted , easily lost
What is the rule for displacement reactions in group 7?
The atoms higher up the group will displace those lower down e.g Cl2 will displace Br-
What happens when a chlorine atom reacts with bromine ions
-Chlorine displaces bromine
-Cl gains e- (reduced)
-Br(oxidised)
-orange colour will appear (br)
What happens when chlorine atoms reacts with iodide ions
-chlorine displaces iodide
-Cl=reduced=gains e-
-I=oxidised=loses e-
-brown colour will appear
What happens when a bromine atom reacts with iodine ions
-bromine displaces iodide
-Br=reduce=gains e-
-I=oxidised loses e-
-brown colour will appear
Reaction of H2SO4 with sodium salts of haldies..
H2SO4(l) + NaX(s)NaHSO4(s) + HX(g)
(or H2SO4(l) + X-HSO4- + HX(g))
-hydrogen halide produced
-halogens acts as a base
Reduced of H2SO4 to SO2 ,S,H2S
-H2SO4 + 2H+ + 2eSO2 + 2H2O== (S reduced from +6 to +4)
-H2SO4 + 6H+ + 6eS + 4H2O== (S reduced from +6 to 0)
-H2SO4 + 8H+ + 8eH2S + 4H2==(S reduced from 6+ to 2-)
Why is chlorine not oxidised by H2SO4
-Cl-=not a strong reducing agent
-thus only an acid based reaction occurs
-H2SO4 + Cl-HSO4- + HCl
-white fumes of HCL will be seen
-the fumes will turn blue litmus paper red
What happens when Br- and H2SO4 react
-Br- is a better reducing agent and is oxidised
- the sulphur in the H2SO4 is only reduced from +6 to +4 (SO2).
-The acid-base reaction=H2SO4 + Br-HSO4- +
-H2SO4 + 2H+ + 2Br-SO2 + Br2 + 2H2O (redox reaction)
What happens when I- and H2SO4 react
-I- is a good reducing agent and is oxidised
The acid-base reaction
: H2SO4 + I-HSO4- + HI
Redox:
-H2SO4 + 6H+ + 6I-S + 3I2 + 4H2O (sulphur reduced to 0)
-H2SO4 + 8H+ + 8I-H2S + 4I2 + 4H2O(sulphur reduced to 2-)
-H2SO4+ 2I-+2H+SO2 + 2H20 + I2
Observation of HSO4 with Br-
-white fumes hat turn blue litmus paper red
-red/orange colour of Br2
Observation of reactions of H2SO with I-
- White fumes which will turn blue litmus paper red
-purple colour of I2 vapour
-smell of rotten eggs due o H2S
What do you use to test for halide ions
Silver nitrate solution
What precipitate do you get when you react with Ag+ with Cl-,Br-,I-?
Cl-=white ppt
Br-=cream ppt
I-=yellow ppt
Why do you add nitric acid when testing for Halide ions
Remove impurities,
Carbonates ,hydroxides = removed as c02 and 0H
Why do we have a further reaction to distinguish between halides after Ag+ is used
The ppt are similar in colour
AgCl dilute/concentrated NH3 observation
Ppt dissolves
AgBr + concentrated NH3 observation
Ppt dissolves with concentrated but not dilute
AgI + NH3 observation
Ppt does not dissolve for dilute or concentrated
Why is the reaction of Cl2 with H2O useful?
Makes HCLO (chloric acid) which is effective at killing bacteria:
-used in water to sterilise eg swimming pools
-Small doses as Cl is toxic
Symbol Equation of Cl2 +H20
-Cl2(g) + H2O(l) == HCl(aq) + HClO(a
-chlorine is oxidised and reduced:
-Cl2= 0
-HCL=-1
-HCLO=+1
How is bleach made?
Chlorine and NaOH
What is the equation for the formation of bleach?
2NaOH + Cl2 -> NaClO +NaCl + H2O
What is formed when AgBr dissolves in excess ammonia?
Ag(NH3)2+ + Br-
