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Rusting process
Rusting process
Necessary conditions of Rusting
1. Presence of oxygen (or air)2. Presence of water
Rusting process
)oxideiron(III)hydratedvarious(
423
)()(
232
)(232)(232)(232iondecomposit
)(3)(2)()(2)(2)(2)(2
(s)
sss
sOHO
sOHO
s
OxHOFe
OHOFeorOHOFeorOHOFe
OHFeOHFeFe lglg
Rusting process
Conditions that accelerate rusting
1. Presence of a strong electrolyte (e.g. salt solution - a good conductor)
2. Presence of a less reactive metal e.g Sn, Cu3. Presence of acid4. Bent or Sharp angled iron article
The speed of rusting canbe monitored by a yellowrust indicator which will turn blue in the presence of rust (Fe2+
(aq) ion).
Presence of strong electrolyte (e.g. sea water)
Strong electrolyte enhances the conductivity of the solution and speeds up the rusting process.
Presence of less reactive metal (e.g. Sn, Zn) A scratched tin-plated iron can rusts mo
re quickly than an ordinary iron can.
Presence of less reactive metal (e.g. Sn, Cu)
Why does a scratched tin-plated iron can rust more quickly than an ordinary iron can ?
As tin is less reactive than iron, iron will lose electrons through tin at a faster speed than if tin is absent. Therefore, the can will rust more quickly.
Presence of acid
In the presence of acid, Fe(s) forms Fe2+(a
q) ions more readily and rusts faster.
Fe(s) + 2H+(aq) Fe2+
(aq) + H2(g)
Conditions accelerate rusting1. Presence of a strong electrolyte
(e.g. salt solution - a good conductor)2. Presence of a less reactive metal e.g Sn, Cu3. Presence of acid4. Bent or Sharp angled iron article
The speed of rusting canbe monitored by a yellowrust indicator which will turn blue in the presence of rust (Fe2+
(aq) ion).