Group 7 Flashcards
What is the trend in bp down group 7?
Increases down group
Size of atom increases as more occupied electron shells so stronger van der waals forces of attraction between molecules
Trend in electronegativity down group 7
Decreases
More occupied shells so greater atomic radius and outer electrons are future away from nucleus so lower force of attraction between the nucleus and electron pair in covalent bond
What do you use to test for halide ions?
Acidified AgNO3
Why do you add HNO3 and not HCl
To remove CO32-
Adding HCl would add Cl- giving a false positive
Result from
Ag+ + Cl- -> AgCl
White ppt
Result from
Ag+ + Br- -> AgBr
Cream ppt
Result from
Ag+ + I- -> AgI
Yellow ppt
What happens to each of the silver haloes precipitates when dilute and concentrated NH3 are added
AgCl dissolve in them both
AgBr dissolves in only concentrated
AgI doesn’t dissolve
What is the trend in oxidising ability down the group
Decreases
Cl has fewest occupied electron shells, greatest force of attraction between outer electrons and nucleus, easier to gain electrons and be reduced so best oxidising agent
What is the trend in reducing ability of the halides down the group
Increases down the group
I- has the most occupied electron shells, so outer electrons are further away from nucleus, weakest force of attraction so easiest to be oxidised and lose electrons
Beat reducing agent
Why is chlorine added to drinking water
Kills microorganisms
Once it has done its job little remains
Benefits outweigh the risk
Risks of adding chlorine to drinking water
It is toxic and can damage the respiratory system
Why is ozone not used to purify water
Exspensive and evaporates fron water quickly
Reaction of Cl2 and water
Cl2 + H2O -> HClO + HCl
What type of reaction is the reaction between Cl and water
Disproportionation
