group 7 Flashcards
electroneg trend
decreases down due to incr atomic structure and shielding
mp and bp
incr down group as molecules larger, more electrons, larger vdw
oxidising ability
decreases down group, become reduced
displacement strength
chlorine displaces bromine and iodide, bromine displaces iodide ions
ionic displacement equations
eg cl2 +2nabr -> br2 +2nacl
cl2 +2br->br2 +2cl-
using silver nitrate to detect which metal present
fluoride- no ppt
chloride- white ppt ag+ +cl- ->agcl
bromide - cream ppt
idide- yellow ppt
if colors hard to see add ammonia
silvermetal ppt and ammonia
[ag(nh3)2]+ + metal-
the silver ammonia thing is colorless
BUT silver iodide is insoluble
sodium fluroide and h2s04
naf + h2so4 ->nahso4 +hf acid base
white steamy fumes
sodium chloride and h2so4
nacl +h2s04 -> nahso4 +4cl acid base
white steamy fumes
sodium bromide and h2s04
nabr +h2so4 ->nahso4 +hbr acid base (1)
2hbr +h2so4->br2 +so2+2h20 redox (2)
(1) white steamy fumes of hbr
(2) red bromine fumes colorless gas
chlorine w water
cl2 +h20->hclo +hcl
used to purify water
disproportionation
chlorine w water and sunlight
2cl2 +2h20 -> 4hcl +02
ionic ; 2cl2 + 2h20 -> 4h+ +4cl- + 02
sodium/calcium chlorate w water
naclo + h20 -> na+ +oh- +hclo
in alkaline solution equilibrium moves to left
chlorine w cold dilute naoh
cl2 + 2naoh ->nacl +naclo +h20
br2 and i2 will react same
test for sulfate ions
The test for sulfate ions makes use of the insoluble properties of barium sulfate.
The solution of the ions under test have a solution of barium chloride which has been acidified using hydrochloric acid.
If a white precipitate appears this is indicative of the presence of sulfate ions.
Ba2+(aq) + SO42-(aq) BaSO4(s)
