AS Level The Halogens
What would you observe if acidified silver nitrate was added to a solution containing iodide ions
a yellow precipitate would be observed
What would you observe is concentrated ammonia solution was added to a precipitate of silver iodide
no visible change
What would you observe is dilute ammonia solution was added to a precipitate of silver bromide
no visible change
Describe an experiment to demonstrate the oxidising ability of the halogens
1. add the halogens to aqueous solutions of the halides and observe the reactions 2. chlorine will displace bromine and iodine 3. bromine will only displace iodine 4. iodine can not displace chlorine or bromine
Describe the trend in reducing ability of the halides
1. as the halide ions get bigger, the attraction between the outer energy level of electrons and the positive nucleus becomes weaker as there is more shielding. 2. This results in the outer energy level electrons being more easily donated. 3. reducing ability of the halide ions increase
What happens when chlorine is bubbled into cold water under UV light?
2Cl2 + 2H2O -> O2 + 4HCl
What happens when chlorine is bubbled into sodium hydroxide
Cl2 + 2NaOH -> NaCl + NaClO + H2O NaClO is bleach, sodium chlorate(I)
What would you observe if acidified silver nitrate was added to a solution containing bromide ions
a cream precipitate would be observed
What is a reducing agent
a reducing agent is an electron donor
What would you observe if acidified silver nitrate was added to a solution containing chloride ions
a white precipitate would be observed
Describe an experiment to demonstrate the reducing ability of the halides
add conc. sulfuric acid to solid samples of the sodium halides sodium chloride: an acid-base reaction occurs where chloride ions gain hydrogen ions to form gaseous hydrogen chloride - misty fumes are observed sodium bromide: a redox reaction occurs, as well as the acid-base reaction described above bromide ions are oxidised to bromine molecules sulfur (VI) in sulfate is reduced to sulfur (IV) in sulfur dioxide sodium iodide: several redox reactions occur, as well as the acid-base reaction described above iodide ions are oxidised to iodine molecules sulfur (VI) in sulfate is reduced to sulfur (IV) in sulfur dioxide sulfur (VI) in sulfate is reduced to sulfur (0) sulfur (VI) in sulfate is reduced to sulfur (-II) in hydrogen sulfide
State the trend in oxidising ability of the halogens down the group
an oxidising agent is an electron acceptor 1. as you down the group, the nuclear charge increases but so does distance and shielding. These outweigh the increase in nuclear charge 2. the attraction between the nucleus and the incoming electrons this decrease, so oxidising ability decreases down the group
State and explain the trend in electronegativity down the group
as you go down the group 1. nuclear charge increases but 2. distance and shielding also increase. 3. These outweigh the increase in nuclear charge The attraction between the nucleus and the bond pair of electrons thus decreases 4. electronegativity decreases
Why is chlorine added to drinking water
chlorine kills microbes, making the water safer to drink
What would you observe is dilute ammonia solution was added to a precipitate of silver iodide
no visible change
Which combination of reagents is used to test for halide ions
silver nitrate in nitric acid
What would you observe is concentrated ammonia solution was added to a precipitate of silver bromide
the cream precipitate would redissolve
Define the term electronegativity
the power of a nuclei to attract a bonding electron pair towards itself in a covalent bond
What would you observe is concentrated ammonia solution was added to a precipitate of silver chloride
the white precipitate would redissolve
What would you observe is dilute ammonia solution was added to a precipitate of silver chloride
the white precipitate would redissolve
Why is the silver nitrate acidified
to remove ions that may interfere with the test, namely carbonate and hydroxide ions
Why can we add chlorine to drinking water
we add just enough to kill the microbes, but not enough to harm those drinking the water
What happens when chlorine is bubbled into water
when chlorine is bubbled into water, a disproportionation reaction occurs. Cl2 + H2O ⇌ HCl + HClO The HCl is an acid, and will turn blue litmus red The HClO is a bleach, and will turn the red litmus paper white
