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