CL 8- halogens Flashcards
Cl₂ appearance
state and colour
pale green gas
Br₂ appearance
state and colour
yellow/orange liquid
I₂ appearance
state and colour
shiny black-grey solid
boiling points of Cl₂, Br₂ and I₂
trend
- increase as you go down the group
- more electrons so therefore
- larger london forces between the molecules
- stronger forces need more energy to overcome
reactivity down group 7
- decreases
- atomic radius increases so
- more inner shells which leads to more shielding
- weaker nuclear attraction, harder to gain an electron
equation to show how chlorine is used in water purification
Cl₂ + H₂O –> HCLO + HCL
equation to show how chlorine reacts with solid, dilute aqueous NaOH to form bleach
Cl₂ + 2NaOH –> NaCLO +NaCl + H₂O
benefits of chlorine use in water treatment
- kills bacteria
- prevents diseases like typhoid and cholera
- makes water fit to drink
risks of chlorine use in water treatment
- chlorine is a toxic gas
- could react with hydrocarbons to form chlorinated hydrocarbons, suspected cause of cancer
Cl₂ + Br⁻
colour change and with cyclohexane
colour change to yellow as Br₂ formed (chlorine displaces as more reactive)
cyclohexane added- orange top layer
Cl₂ + I⁻
colour change and with cyclohexane
colour change to brown as I₂ formed (chlorine displaces as more reactive)
cyclohexane added- purple top layer
Br₂ + Cl⁻
colour change and with cyclohexane
stays yellow/orange (no displacement)
cyclohexane- orange top layer
Br₂ + I⁻
colour change and with cyclohexane
colour change to brown as I₂ formed (bromine displaces as more reactive)
cyclohexane- purple top layer
I₂ + Cl⁻
colour change and with cyclohexane
stays brown (no displacement)
cyclohexane- purple top layer
Br₂ + I⁻
colour change and with cyclohexane
stayed brown (no displacement)
cyclohexane- purple top layer
