chapter 4 (group 7) Flashcards
(12 cards)
at room temperature what are the states of the halogens
fluorine-gas
chlorine-gas
bromine-liquid
iodine-solid
whats the trend in electronegativity in group 7 and explain why it is
fluorine is the most electronegative element oat
electronegativity decreases down the group
-because atomic radius increases so less attraction to the electrons
-electrons become further away from the nucleus so have less attraction to the nucleus
-therefore less electronegativity
explain the trend in group 7 boiling points
increases down the group
because elements have more electrons so more van der Waals forces
stronger van der Waals mean stronger intermolecular forces-therefore higher boiling point
what do the silver halides do in ammonia
all silver halides precipitate out of aqueous solution
when ammonia is added, they may dissolve again
solubility increases down group 7
whats the trend of oxidising and reducing ability of halogens
oxidation decreases down the group-same as electronegativity
reducing ability increases down the group- iodine is the most, and fluorine doesn’t reduce at all
explain halogen displacement reactions. use Cl2 +NaBr
if an elemental halogen is added to a halide solution, the heavier halide will be displaced
this is because the lighter halide will have a greater preference to be the halide ion because it is more electronegative
Cl2 + NaBr = NaCl + Br
explain halogen reactions with sulfuric acid H2SO4
halides react with sulfuric acid differently because of their reducing ability
reaction with a fluoride or chloride produces HF or HCl
reaction with a bromide produces some Br2 and some So2
reaction with an iodide produces iodine immediately and will reduce the sulfur to H2S
how to identify the halides
add silver nitrate to the solution of halide ions, the halide will react with the silver cations
Ag+(aq) +Br-(aq) = AgBr(s)
a precipitate is formed with a specific colour for each halide
what are the colours of each halide when reacted with silver
AgCl= white ppt
AgBr= cream ppt
AgI= yellow ppt
how to identify the halides using ammonia
use the silver halide and re-dissolve it in ammonia
AgCl should re-dissolve
AgBr should re-dissolve slowly and will require a lot of ammonia
AgI should not dissolve
how does chlorine react with water and water with sunlight
water only:
Cl2 + H2O = HCl + HClO = 2H+ +CLO- +Cl-
used to kill bacteria in water
water and sunlight:
the same reaction will happen but there is a further step
2HClO = 2HCl + O2
so the overall equation will be
2CL2 +2H2O =4HCl +O2
explain the reaction between Cl2 and sodium hydroxide
the products are sodium chlorate(i) and sodium chloride
chlorine is disproportionated- both oxidised and reduced
