Group 7 reducing power Flashcards
When do halogens act as reducing agents (become oxidised themselves?
They are oxidised in displacement reactions when halide ions in a salt are displaced (lose these electrons) by more reactive halogen to form a halogen molecule
What do halogens usually act as?
Oxidising agents because they make other elements lose electrons (oxidised) to complete outer shell and be reduced
Trend of halide ions reducing power ?
It will increase down the group
What is reducing power?
The ability for halide ions to lose electrons and be OXIDISED but REDUCE ANOTHER ELEMENT!!!
Why do halide ions reduce and be oxidised?
To go from halide ion (with a negative charge) lose these electrons to form pure halogen
Why does reducing power of halide ions increase down the group?
This is ability to lose outer shell electrons (oxidised)
As ionic radii increases, electrons at further distance from nuclei
And more electrons shield outer electrons
So electrons experience less nuclear attraction and lost easier
(Overcomes increase in nuclear charge)
What does the halide ions increasing reducing power coincide with? And why?
Ionisation energy because going down group, easier to remove electron (lower IE)
And so reducing power increases (ability to lose electrons)
What is most strongly reducing halogen?
Iodine loses electrons easiest
Most strongly oxidising halogen?
Fluorine gains electrons easiest
Sulfuric acid + KCl or KF
Forms KHSO4 and HF/HCl
Reaction STOPS HERE
Sulfuric acid + KBr
Forms KHSO4 + HBr
HBr + H2SO4 forms SO2 + Br2 + H2O
Reaction stops here
Sulfuric acid + KI
Forms KHSO4 + HI
HI + H2SO4 forms SO2 + I2 + H2O
HI+ SO2 forms H2S + I2 + H2O
Why do certain halide ions continue to react when added to sulfuric acid?
Because going down, the reducing ability increases down the group
So is easier to be oxidised and reduce the H2O4/ the SO2
What does ammonia + hydrogen halide form?
An ammonia salt eg NH4Cl
NOT A REDOX REACTION
