2.3 halogens Flashcards
physical properties of the first 4 halogens
fluorine: pale yellow gas
chlorine: green gas
bromine: red-brown liquid
iodine: grey solid
trend of boiling point down group 7
increases down the group.
molecules get larger as you go down the group so they will have stronger van der waal forces.
which need more energy to break
trend in electronegativity down group 7
decreases down the group.
atomic radius increases down the group due to increase number of shells.
the nucleus therefore is less able to attract the bonding pair of electrons
trend of reactivity down group 7
decreases down the group.
atomic radius increases in size due to more shells.
electrons are further from the nucleus.
there is a weaker electrostatic force of attraction between the electron + nucleus.
so it is harder for larger halogens to attract electrons and form a full outer shell
trend of oxidising power down group 7
decreases down the group.
as it is harder for larger halogens to attract electrons their ability to be oxidising agents decreases
reaction between chlorine + bromide/iodide
chlorine will displace both halogens as it is the strongest oxidising agent
equation + observation between chlorine + bromide/iodide
Cl2+ 2Br- ➔ 2Cl-+ Br2
yellow solution
Cl2 + 2I- ➔ 2Cl- + I2
brown solution
reaction between bromine + chloride/iodie
bromine will displace iodide as it is a stronger oxidising power, but will not displace chloride
equation and observation between bromine + iodide
Br2 + 2I- ➔ 2Br- + I2
brown solution
ionic oxidation equation for bromide
2Br- ➔ Br2 + 2e-
ionic reduction equation for chlorine
Cl2 + 2e- ➔ 2Cl-
trend of reducing agent down group 7
increases down the group.
more electron shells, larger atomic radius, outer electrons further away from the nucleus, weaker electrostatic force of attraction, easier for larger halide ions to lose electrons
test for halide ions
1.adding nitric acid (HNO3) to sample - to remove any carbonates.
2. add silver nitrate (AgNO3) to form a halide precipitate
observation of each halide precipitate
Cl- = white precipitate
Br- = cream precipitate
I- = yellow precipitate
further steps to identify AgCl
add dilute ammonia to AgCl
forms a complex ion and a colourless solution
equation when dilute NH3 is added to AgCl
AgCl (aq) + 2NH3 (aq) ➔ [Ag(NH3)2]+ (aq) + Cl- (aq)
further steps to identify AgBr
add conc ammonia to AgBr
forms a complex ion and a colourless solution
equation when conc NH3 is added to AgBr
AgBr (aq) + 2NH3 (aq) ➔ [Ag(NH3)2]+ (aq) + Br- (aq)
why does adding dilute NH3 to AgBr + AgI and conc NH3 to AgI have no reaction
they remain insoluble
observation when H2SO4 is added to NaF or NaCl + what type of reaction is it
white steamy fumes or HF or HCl
acid-base reaction
equations for the reaction between NaF/NaCl + H2SO4
NaF(s) + H2SO4 (l) -> NaHSO4 (s) + HF(g)
NaCl(s) + H2SO4 (l) -> NaHSO4 (s) + HCl(g)
observation when H2SO4 is added to NaBr (acid-base)
white steamy fumes of HBr
equations for the reaction between NaBr + H2SO4
NaBr(s) + H2SO4 (l) ->NaHSO4 (s) + HBr(g)
observation between HBr + H2SO4 (redox)
orange fumes of bromine + colourless gas SO2
