2.3 Group 7 Flashcards
Reducing agent definition
Electron donor
What is the reducing strength of halides?
- Increases as you go down the group
- Ionic radius increases
- Weaker attraction between outer electrons and nucleus
Write the half equation for iodine
I- –> I2
Write the three half equation for H2SO4
H2SO4 –> SO2
H2SO4 –> S
H2SO4 –> H2S
What happens when fluoride or chloride react with H2SO4?
They are too weak as reducing agents so undergo acid-base reactions instead
H+ + F- –> HF
Misty fumes of Hf gas
H+ + Cl- –> HCl
Misty funds of HCl gas
What is the test for halides?
- Dissolve sample in water
- Add HNO3 acid
- Add AgNO3 solution
- If a halide is present then
fluoride - no precipitate
chloride - white precipitate
bromide - cream precipitate
iodide - yellow precipitate - Add dilute NH3 to the sample
chloride - white ppt dissolves
bromide - cream ppt insoluble
iodide - yellow ppt insoluble - Add concentrated NH3 to the sample
bromide - cream ppt dissolves
iodide - yellow ppt insoluble
Why do you add HNO3 acid in the halide test?
To remove any possible CO3 2- impurities that would give a false positive
Oxidising agent definition
Electron acceptor
Trend in oxidising ability of halogens
Decreases down the group
Larger radius
Weaker attraction between uncles and incoming electron
Why can F2 not be used in displacement reactions?
Its so reactive that it will react with the water dissolving the halide compound
What is the ionic equation for chlorine + sodium bromide?
Chlorine + sodium bromide –> Bromine + Sodium chloride
Cl2 + 2Br- –> 2Cl- + Br2
What is the ionic equation for chlorine + sodium iodide?
Chlorine + Sodium iodide –> Iodide + Sodium Chloride
Cl2 + 2I- –> 2Cl- + I2
What is the ionic equation for bromine + sodium iodide?
Bromine + Sodium iodide –> Iodide + Sodium bromide
Br2 + 2I- –> 2Br- + I2
