✔ 最佳答案
1.
The rusting of iron can be divided into the following stages:
Stage 1: Fe(s) → Fe2+(aq) + 2e-
Stage 2: Fe2+(aq) → Fe3+(aq) + e-
Stage 3: 2Fe3+(aq) + ….. → Fe2O3nH2O(s)
The electrons needed in stages 1 and 2 are gained by the following reduction:
O2(g/aq) + 2H2O(l) + 4e- → 4OH-(aq)
Rusting involves the transfer of electrons. In an electrolyte, there are mobile ions, which carry charges, can enhance the transfer of electrons and thus acceleration the reaction.
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2.
What is a base, and what is an acid? There are a lot of theories (or concepts) to define what acids and bases are:
(1) Arrhenius' theory of acids and bases
An acid is a substance which can give off H+(aq) ions in water.
e.g. HCl(aq) → H+(aq) + Cl-(aq)
A base (actually, an alkali) is a substance which can give off OH-(aq) ions in water.
e.g. NaOH(s) + aq → Na+(aq) + OH-(aq)
In CE level, only Arrhenius' theory is used.
(2) Bronsted-Lowry theory of acids and bases
An acid is a proton (i.e. H+ ion) donor in a proton-transfer reaction.
e.g. HCl → H+ + Cl-
A base is a proton acceptor in a proton-transfer reaction.
e.g. NH3 + H+ → NH4+
(3) Lewis theory of acids and bases
An acid is an electron-pair acceptor in formation of dative bond.
A base is an electron-pair donor in formation of dative bond.
e.g.1 H+ + OH- → H←OH
e.g.1 H+ is an acid and OH- is a base.
e.g.2 BF3 + NH3 → F3B←NH3
e.g.2 BF3 is an acid and NH3 is a base.
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