1
Q
where in a water droplet is the [O2] the highest?
A
the edges of the droplet
2
Q
what two half equations are involved in rusting?
A
O2 + 2H2O + 4e –> 4OH-
Fe –> 2e- + Fe2+
3
Q
chemical formula for rust
A
Fe2O3.XH2O
4
Q
three ways to prevent rusting
A
sacrificial protection - use a more reactive metal, it will be preferentially oxidised
galvanising - thin layer of zinc (turns into ZnO) over the metal, if this is stratched zinc reacts in preference to Fe
barrier protection - stops O2 AND H2O reaching the surface of the metal
5
Q
why is rusting worse near the sea?
A
NaCl increases the conductivity of the water
6
Q
what must be present for rusting to occur?
A
Fe, O2, H2O
developing metals
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