redox reactions & reactivity Flashcards
what happens to the halogen’s oxidising power as you go down the group?
decreases
- ability to attract electrons decreases due to shielding and a greater atomic radius
what does the relative oxidising power of halogens mean?
a halogen will displace any halogen beneath it
what are halide ions?
negative ions
- good reducing agents
reducing power increases down the group
what do redox reactions depend on?
the reducing strength of the halide
describe the reaction between chloride ions and chlorine
no reaction
colourless
describe the reaction between bromide ions and chlorine
Cl displaces Br
aq layer is yellow
organic layer stays orange
describe what happens when a halogen is added to an organic solvent
- dissolves
- forms a layer
- ABOVE the aq organic layer
what is the use of hexane in displacement reactions?
makes observing colour change easier
describe the reaction between iodide ions and chlorine
Cl displaces I
aq layer is yellow
organic layer stays purple
describe the reaction between bromide ions and chlorine
no reaction
describe the reaction between bromide ions and iodine
Br displaces I
aq layer is orange
organic layer stays purple
what is a disproportionation reaction?
where the species is both oxidised and reduced
what is the disporoportionation reaction of chlorine and cold water?
Cl2 + H2O –> ClO- + Cl- + 2H+
ClO- = +1
Cl- = -1
what reaction forms bleach?
disproportionation with cold dilute sodium hydroxide
how is the formation of bleach a disproportionation reaction?
Cl is simultaneously oxidised & reduced
what is bleach used for?
- treat water
- bleach paper
- cleaning agent
what is meant by water sterilisation?
adding Cl to kill bacteria
state 3 advantages of chlorinating water
- destroys micro organisms that cause disease
- long lasting as reduces bacteria build up down supply
- reduces algae growth
state 3 disadvantages of chlorinating water
- Cl gas is toxic and irritates respiratory system
- liquid Cl causes chemical burns
- Cl reacts with organic compounds to make chloroalkanes which can cause cancer
what are the alternatives to chlorinating water?
ozone = oxidising agent which kills microrganisms
- short half life so not permanent
- expensive
UV = damages microorganisms DNA
- ineffective in cloudy water
- won’t prevent further contamination
