化學 2000 年 DSE、CE 選擇題（第 3 頁）

21.

In an experiment, a piece of calcium metal was added to a beaker of water. Which of the following statements concerning the experiment is/are correct ?

(1)The calcium metal sinks to the bottom of the beaker.

(2)The calcium metal burnt with brick red flame.

(3)At the end of the experiment, an alkaline solution was formed in the beaker.

22.

Which of the following statements concerning helium is/are correct ?

(1)The outermost electron shell of a helium atom has an octet structure.

(2)Helium is used to fill weather balloons.

(3)Helium exists as monatomic molecules.

23.

Consider the chemical cell shown below:

Which of the following statements concerning the cell is/are correct ?

(1)Oxidation takes place at the copper electrode.

(2)The concentration of magnesium ions in beaker X increases.

(3)The salt bridge allows electrons to flow from one electrode to the other electrode.

24.

Which of the following polymers is/are made by condensation polymerization ?

25.

Some concentrated sulphuric acid was poured into a sink connected to a catchpot made of polyvinyl chloride (PVC). After some time, the catchpot becomes deformed. Which of the following explanations for the deformation of the catchpot is/are correct?

(1)The heat liberated when the concentrated sulphuric acid mixed with the water in the catchpot caused PVC to soften.

(2)PVC was decomposed into its monomer by the concentrated sulphuric acid.

(3)PVC was oxidized by the concentrated sulphuric acid.

26.

X is an element in Group VI of the Periodic Table. X can form X²⁻ ions. Which of the following statements are correct ?

(1)The oxidation number of X decrease when X²⁻ ion is formed.

(2)Both X atom and X²⁻ ion have the same number of electron shells.

(3)Both X atom and X²⁻ ion have the same nuclear charge.

27.

Which of the following measures can reduce the emission of pollutants from a coal-fired power station?

(1)installation of scrubbers

(2)installation of electrostatic precipitators

(3)increasing the height of the chimney

28.

Which of the following statements concerning soaps are correct ?

(1)They are esters.

(2)They can reduce the surface tension of water.

(3)Their aqueous solutions are alkaline.

29.

Which of the following statements concerning carbon, silicon and phosphorus are correct ?

(1)Carbon forms numerous compounds with hydrogen and oxygen.

(2)Silicon is used to make computer chips.

(3)Phosphorus is an essential element for plant growth.

30.

Which of the following statements concerning a zinc-carbon cell are correct ?

(1)The ammonium chloride in the cell acts as an electrolyte.

(2)The manganese(IV) oxide in the cell acts as an oxidizing agent.

(3)The zinc case of the cell acts as the positive terminal.