兩條f.4 chem,關於acid reaction

1.點解concentrat sulphuric acid同metal react 時會出sulphur dioxide??
Concentrated sulphuric acid, when heated, is an oxidizing agent. Copper is a reducing agent, although its reducing power is not strong. Therefore, redox reaction occurs when concentrated sulphuric acid reacts with copper. Concentrated sulphuric acid (oxidation number of S = +6) is reduced to sulphur dioxide (oxidation number of S = +4), while copper (oxidation number of Cu = 0) is oxidized to copper(II) ion (oxidation number = +2).


2.very dilute nitric acid加copper有咩反應??
Very dilute nitric acid does not react with copper. This is because very dilute nitric acid does not have oxidizing power and the reactivity of copper is too low to react with very dilute nitric acid.
(Very dilute nitric acid can react with a metal, which is more reactive than copper, to give hydrogen gas.)

2011-02-02 17:10:26 補充：
1.
The equation of the reaction between copper and concentrated sulphuric acid:
Cu + 2H2SO4 → CuSO4 + 2H2O + SO2

2011-02-02 17:10:32 補充：
The reaction of concentrated sulphuric acid with magnesium is similar to that with copper. However, magnesium is much more reactive than copper, and thus heating is not needed when magnesium is used. The equation is:
Mg + 2H2SO4 → MgSO4 + 2H2O + SO2